fix: add a Settings toggle for known-symbol spoof verification (closes #176)

The README promises all four token-spam filters "default to on but can be
individually disabled". Known-symbol spoof verification had no state flag, no
checkbox and no consulted setting: filterTransactions() applied it before any
filter setting was read, so three of the four documented filters were
configurable and the fourth was mandatory.

Adds hideSpoofedSymbols, default on, persisted and migrated so a profile
written before the setting existed loads it as on rather than undefined. The
flag is fail-safe in the pure function too: only an explicit false disables
the check, so a caller that omits the key keeps it.

Turning the setting off also stops the fraud-contract learning. That learning
is fed only by this check, and leaving it on would make the setting a no-op:
the contract it recorded would hide the very row the user asked to see, via
the fraud-contract rule that is on by default.

Scope: the setting governs the transaction history. The same check on the
balance list and the send-screen token selector stays unconditional — those
decide which tokens the user can act on, not what the history displays. The
README's user-configurable paragraph now states what each of the four
settings actually reaches, which is not uniform.

The two `current behaviour:` tests pinning the filter as undisableable are
inverted rather than deleted, and joined by coverage for the bypass, the
halted learning, the untouched sibling rules and the storage round-trip.

README.md

@@ -720,6 +720,7 @@ screen, including ExportPrivKey, falls back to Home.
     - Blockscout API: endpoint URL input + "Save" button (validated against
       `/stats` before being saved)
     - Token Spam Protection:
+        - "Hide fake tokens impersonating a known symbol" checkbox
         - "Hide tokens with fewer than 1,000 holders" checkbox
         - "Hide transactions from detected fraud contracts" checkbox
         - "Hide dust transactions below N gwei" checkbox + threshold input
@@ -1081,7 +1082,19 @@ indexes it as a real token transfer.
   a spoof and filtered from display. The fake "Ethereum" token in the attack
   above used symbol "ETH" from contract
   `0xD05339f9Ea5ab9d9F03B9d57F671d2abD1F55c82`, which does not match the known
-  WETH contract — so it would be caught by this check.
+  WETH contract — so it would be caught by this check. Detecting a spoof is also
+  what adds a contract to the fraud contract blocklist below; that is the only
+  thing that populates it. In the transaction history the check is the "Hide
+  fake tokens impersonating a known symbol" setting, on by default; with it off,
+  spoofed transfers are shown and no new blocklist entries are learned from
+  them. The send-screen token selector applies the same check unconditionally,
+  because it decides which tokens the user can act on rather than what the
+  history displays. The balance list applies it unconditionally too, but not
+  identically: it exempts symbols that `KNOWN_SYMBOLS` maps to `null`, and
+  `"ETH"` is the only one. So the fake "Ethereum" token above is filtered from
+  the transaction history and from the send selector, but a fake-`ETH` ERC-20
+  that clears the balance list's own 1,000-holder floor — or that the user
+  tracked manually — is still shown in the balance list.
 
 - **Low-holder token filtering**: Token transfers from ERC-20 contracts with
   fewer than 1,000 holders are hidden from transaction history by default.
@@ -1108,13 +1121,22 @@ indexes it as a real token transfer.
   it. AutistMask hides transactions below a configurable dust threshold
   (default: 100,000 gwei / 0.0001 ETH). This is high enough to filter poisoning
   dust while low enough to preserve any transfer a user would plausibly care
-  about. The threshold is user-configurable in Settings.
+  about. The threshold is user-configurable in Settings; a threshold of `0`
+  hides nothing, exactly as clearing the checkbox does.
 
-- **User-configurable**: All of the above filters (known symbol verification,
-  low-holder threshold, fraud contract blocklist, dust threshold) are settings
-  that default to on but can be individually disabled by the user. AutistMask is
-  designed as a sharp tool — users who understand the risks can configure the
-  wallet to show everything unfiltered, unix-style.
+- **User-configurable**: All four filters (known symbol verification, low-holder
+  threshold, fraud contract blocklist, dust threshold) are settings that default
+  to on but can be individually disabled by the user. AutistMask is designed as
+  a sharp tool — users who understand the risks can configure the wallet to show
+  everything unfiltered, unix-style. All four settings govern the transaction
+  history; what else each one reaches varies. The known-symbol check also runs
+  unconditionally on the send-screen token selector, and on the balance list
+  except for symbols mapped to `null` (`"ETH"` alone), which the balance list
+  does not filter. The fraud contract blocklist is applied unconditionally on
+  that selector and is not consulted by the balance list at all. The low-holder
+  setting also gates the send selector, while the balance list's own
+  1,000-holder floor is unconditional (see Data Model). The dust threshold
+  applies to the transaction history alone.
 
 #### Phishing Domain Protection
 

TODO.md

@@ -44,6 +44,15 @@ undefined identifiers, which is how
 
 # Completed Steps
 
+- 2026-08-11: Known-symbol spoof verification became a Settings toggle
+  (`hideSpoofedSymbols`), on by default, governing the transaction-history
+  filter and the fraud-contract learning it feeds
+  ([#176](https://git.eeqj.de/sneak/AutistMask/issues/176)).
+- 2026-08-11: A dust threshold of `0` now means "hide nothing" instead of
+  falling back to the 100,000 gwei default, and every address comparison in
+  `src/shared/transactions.js` goes through one case-normalising helper so a
+  checksummed genuine contract is no longer read as a spoof
+  ([#179](https://git.eeqj.de/sneak/AutistMask/issues/179)).
 - 2026-08-11: Policy compliance sweep — conditional verbose test rerun, local
   Tailwind binary instead of `npx`, `--frozen-lockfile` on `make install`, and
   the Makefile-only targets documented in the README

docs/README.md

@@ -323,7 +323,14 @@ by default:
 **Known token symbol verification.** AutistMask ships a list of roughly 500
 legitimate ERC-20 tokens with their contract addresses. If a transaction or
 balance claims to involve a known symbol (like "ETH" or "USDT") but comes from
-an unrecognized contract, it is identified as a spoof and hidden.
+an unrecognized contract, it is identified as a spoof and hidden. In your
+transaction history this is the "Hide fake tokens impersonating a known symbol"
+setting, which you can switch off; doing so also stops new entries being added
+to the fraud contract blocklist below, since detecting a spoof is what fills it.
+The send token list always applies the check. Your balances apply it too, with
+one exception: a token claiming the symbol "ETH" is not filtered there, so a
+fake "ETH" token can still show up in your balance list even though it is hidden
+from your transaction history and from the send token list.
 
 **Low-holder token filtering.** Tokens with fewer than 1,000 holders are hidden
 from transaction history and the send token list, and are left out of your

src/popup/index.html

@@ -948,6 +948,15 @@
                         transfers and prevent interaction with suspicious
                         tokens.
                     </p>
+                    <label
+                        class="text-xs flex items-center gap-1 cursor-pointer mb-2"
+                    >
+                        <input
+                            type="checkbox"
+                            id="settings-hide-spoofed-symbols"
+                        />
+                        Hide fake tokens impersonating a known symbol
+                    </label>
                     <label
                         class="text-xs flex items-center gap-1 cursor-pointer mb-2"
                     >

src/popup/views/addressDetail.js

@@ -148,6 +148,7 @@ async function loadTransactions(address) {
             state.blockscoutUrl,
         );
         const result = filterTransactions(rawTxs, {
+            hideSpoofedSymbols: state.hideSpoofedSymbols,
             hideLowHolderTokens: state.hideLowHolderTokens,
             hideFraudContracts: state.hideFraudContracts,
             hideDustTransactions: state.hideDustTransactions,

src/popup/views/addressToken.js

@@ -222,6 +222,7 @@ async function loadTransactions(address, tokenId) {
             state.blockscoutUrl,
         );
         const result = filterTransactions(rawTxs, {
+            hideSpoofedSymbols: state.hideSpoofedSymbols,
             hideLowHolderTokens: state.hideLowHolderTokens,
             hideFraudContracts: state.hideFraudContracts,
             hideDustTransactions: state.hideDustTransactions,

src/popup/views/home.js

@@ -163,6 +163,7 @@ async function loadHomeTxs(ctx) {
     if (allAddresses.length === 0) return;
 
     const filters = {
+        hideSpoofedSymbols: state.hideSpoofedSymbols,
         hideLowHolderTokens: state.hideLowHolderTokens,
         hideFraudContracts: state.hideFraudContracts,
         hideDustTransactions: state.hideDustTransactions,

src/popup/views/settings.js

@@ -284,6 +284,12 @@ function init(ctx) {
         applyTheme(state.theme);
     });
 
+    $("settings-hide-spoofed-symbols").checked = state.hideSpoofedSymbols;
+    $("settings-hide-spoofed-symbols").addEventListener("change", async () => {
+        state.hideSpoofedSymbols = $("settings-hide-spoofed-symbols").checked;
+        await saveState();
+    });
+
     $("settings-hide-low-holders").checked = state.hideLowHolderTokens;
     $("settings-hide-low-holders").addEventListener("change", async () => {
         state.hideLowHolderTokens = $("settings-hide-low-holders").checked;
@@ -304,11 +310,17 @@ function init(ctx) {
 
     $("settings-dust-threshold").value = state.dustThresholdGwei;
     $("settings-dust-threshold").addEventListener("change", async () => {
-        const val = parseInt($("settings-dust-threshold").value, 10);
-        if (!isNaN(val) && val >= 0) {
+        const raw = $("settings-dust-threshold").value.trim();
+        const val = Number(raw);
+        // 0 is accepted and means "hide nothing".  Empty, negative,
+        // fractional and non-numeric input is rejected outright rather than
+        // coerced, and the field is put back to the stored threshold so it
+        // never shows a value the wallet is not using.
+        if (raw !== "" && Number.isInteger(val) && val >= 0) {
             state.dustThresholdGwei = val;
             await saveState();
         }
+        $("settings-dust-threshold").value = state.dustThresholdGwei;
     });
 
     $("settings-utc-timestamps").checked = state.utcTimestamps;

src/shared/state.js

@@ -21,6 +21,7 @@ const DEFAULT_STATE = {
     deniedSites: {},
     rememberSiteChoice: true,
     showZeroBalanceTokens: true,
+    hideSpoofedSymbols: true,
     hideLowHolderTokens: true,
     hideFraudContracts: true,
     hideDustTransactions: true,
@@ -61,6 +62,7 @@ async function saveState() {
         deniedSites: state.deniedSites,
         rememberSiteChoice: state.rememberSiteChoice,
         showZeroBalanceTokens: state.showZeroBalanceTokens,
+        hideSpoofedSymbols: state.hideSpoofedSymbols,
         hideLowHolderTokens: state.hideLowHolderTokens,
         hideFraudContracts: state.hideFraudContracts,
         hideDustTransactions: state.hideDustTransactions,
@@ -112,6 +114,12 @@ async function loadState() {
             saved.showZeroBalanceTokens !== undefined
                 ? saved.showZeroBalanceTokens
                 : true;
+        // A profile written before this setting existed has no key for it.
+        // It is a safety filter, so absent must load as on, not as undefined.
+        state.hideSpoofedSymbols =
+            saved.hideSpoofedSymbols !== undefined
+                ? saved.hideSpoofedSymbols
+                : true;
         state.hideLowHolderTokens =
             saved.hideLowHolderTokens !== undefined
                 ? saved.hideLowHolderTokens

src/shared/transactions.js

@@ -10,6 +10,14 @@ const { formatEther, formatUnits } = require("ethers");
 const { log, debugFetch } = require("./log");
 const { KNOWN_SYMBOLS, TOKEN_BY_ADDRESS } = require("./tokenList");
 
+// Ethereum addresses are case-insensitive: EIP-55 mixed case is a checksum
+// over the address, not part of its identity.  Every address comparison in
+// this file goes through this helper, so an address arriving in checksummed
+// or upper-case form can never be read as a different address.
+function normalizeAddress(addr) {
+    return (addr || "").toLowerCase();
+}
+
 function formatTxValue(val) {
     const parts = val.split(".");
     if (parts.length === 1) return val + ".0000";
@@ -30,10 +38,10 @@ function parseTx(tx, addrLower) {
     let exactValue = formatEther(rawWei);
     let rawAmount = rawWei;
     let rawUnit = "wei";
-    let direction = from.toLowerCase() === addrLower ? "sent" : "received";
+    let direction = normalizeAddress(from) === addrLower ? "sent" : "received";
     let directionLabel = direction === "sent" ? "Sent" : "Received";
     if (toIsContract && method && method !== "transfer") {
-        const token = TOKEN_BY_ADDRESS.get(to.toLowerCase());
+        const token = TOKEN_BY_ADDRESS.get(normalizeAddress(to));
         if (token) {
             symbol = token.symbol;
         }
@@ -87,7 +95,8 @@ function parseTokenTransfer(tt, addrLower) {
     const to = tt.to?.hash || "";
     const decimals = parseInt(tt.total?.decimals || "18", 10);
     const rawVal = tt.total?.value || "0";
-    const direction = from.toLowerCase() === addrLower ? "sent" : "received";
+    const direction =
+        normalizeAddress(from) === addrLower ? "sent" : "received";
     const sym = tt.token?.symbol || "?";
     return {
         hash: tt.transaction_hash,
@@ -104,11 +113,9 @@ function parseTokenTransfer(tt, addrLower) {
         direction: direction,
         directionLabel: direction === "sent" ? "Sent" : "Received",
         isError: false,
-        contractAddress: (
-            tt.token?.address_hash ||
-            tt.token?.address ||
-            ""
-        ).toLowerCase(),
+        contractAddress: normalizeAddress(
+            tt.token?.address_hash || tt.token?.address || "",
+        ),
         holders: parseInt(tt.token?.holders_count || "0", 10),
     };
 }
@@ -194,7 +201,7 @@ function mergeTransactions(txs, tokenTransfers) {
 
 async function fetchRecentTransactions(address, blockscoutUrl, count = 25) {
     log.debugf("fetchRecentTransactions", address);
-    const addrLower = address.toLowerCase();
+    const addrLower = normalizeAddress(address);
 
     const [txResp, ttResp] = await Promise.all([
         debugFetch(blockscoutUrl + "/addresses/" + address + "/transactions"),
@@ -243,34 +250,45 @@ function isSpoofedSymbol(tx) {
     if (!KNOWN_SYMBOLS.has(symbol)) return false;
     const legit = KNOWN_SYMBOLS.get(symbol);
     if (legit === null) return true; // "ETH" as ERC-20 is always fake
-    return tx.contractAddress !== legit;
+    return normalizeAddress(tx.contractAddress) !== normalizeAddress(legit);
 }
 
 // Pure filter function. Takes raw transactions and filter settings,
 // returns { transactions, newFraudContracts }.
 function filterTransactions(txs, filters = {}) {
     const fraudSet = new Set(
-        (filters.fraudContracts || []).map((a) => a.toLowerCase()),
+        (filters.fraudContracts || []).map(normalizeAddress),
     );
+    // The dust threshold defaults only when it is unset (nullish): a
+    // threshold of 0 is a real value meaning "hide nothing", since no
+    // transaction has a value below 0 gwei.  It is therefore equivalent to
+    // clearing the hide-dust checkbox, and the two controls cannot override
+    // each other in either direction.
+    const dustThresholdGwei = filters.dustThresholdGwei ?? 100000;
     const newFraud = [];
     const filtered = [];
+    // Fail-safe, unlike the three flags below: this one is off only when the
+    // caller says so explicitly, so a caller that omits the key keeps the
+    // check rather than silently losing it.  The setting also governs the
+    // blocklist learning below, which exists only to serve this check —
+    // leaving learning on while the check is off would re-hide the very rows
+    // the user asked to see, through the fraud-contract rule.
+    const hideSpoofed = filters.hideSpoofedSymbols !== false;
 
     for (const tx of txs) {
-        // Always filter spoofed known symbols and record the fraud contract
-        if (isSpoofedSymbol(tx)) {
-            if (tx.contractAddress && !fraudSet.has(tx.contractAddress)) {
-                fraudSet.add(tx.contractAddress);
-                newFraud.push(tx.contractAddress);
+        const contract = normalizeAddress(tx.contractAddress);
+
+        // Filter spoofed known symbols and record the fraud contract
+        if (hideSpoofed && isSpoofedSymbol(tx)) {
+            if (contract && !fraudSet.has(contract)) {
+                fraudSet.add(contract);
+                newFraud.push(contract);
             }
             continue;
         }
 
         // Filter fraud contracts if setting is on
-        if (
-            filters.hideFraudContracts &&
-            tx.contractAddress &&
-            fraudSet.has(tx.contractAddress)
-        ) {
+        if (filters.hideFraudContracts && contract && fraudSet.has(contract)) {
             continue;
         }
 
@@ -291,7 +309,7 @@ function filterTransactions(txs, filters = {}) {
             filters.hideDustTransactions &&
             !tx.isContractCall &&
             tx.valueGwei !== null &&
-            tx.valueGwei < (filters.dustThresholdGwei || 100000)
+            tx.valueGwei < dustThresholdGwei
         ) {
             continue;
         }

tests/state.test.js

@@ -102,3 +102,60 @@ describe("loadState hasWallet reconciliation", () => {
         expect(mod.state.activeAddress).toBe(ADDRESS);
     });
 });
+
+// The known-symbol spoof filter is a safety filter, so an existing profile
+// stored before the setting existed must load with it on rather than with
+// undefined, which would read as off.
+describe("hideSpoofedSymbols persistence", () => {
+    test("defaults to on with empty storage", async () => {
+        const { mod } = loadModuleWith(null);
+        await mod.loadState();
+        expect(mod.state.hideSpoofedSymbols).toBe(true);
+    });
+
+    test("a profile stored without the key loads with it on", async () => {
+        const { mod } = loadModuleWith({ wallets: oneWallet() });
+        await mod.loadState();
+        expect(mod.state.hideSpoofedSymbols).toBe(true);
+    });
+
+    test("an explicit false survives the load", async () => {
+        const { mod } = loadModuleWith({
+            wallets: oneWallet(),
+            hideSpoofedSymbols: false,
+        });
+        await mod.loadState();
+        expect(mod.state.hideSpoofedSymbols).toBe(false);
+    });
+
+    test("saveState persists the flag", async () => {
+        const { mod, set } = loadModuleWith(null);
+        mod.state.hideSpoofedSymbols = false;
+        await mod.saveState();
+        expect(set).toHaveBeenCalledWith({
+            autistmask: expect.objectContaining({ hideSpoofedSymbols: false }),
+        });
+    });
+
+    test("the flag round-trips off through save and load", async () => {
+        const first = loadModuleWith(null);
+        first.mod.state.hideSpoofedSymbols = false;
+        await first.mod.saveState();
+        const persisted = first.set.mock.calls[0][0].autistmask;
+
+        const second = loadModuleWith(persisted);
+        await second.mod.loadState();
+        expect(second.mod.state.hideSpoofedSymbols).toBe(false);
+    });
+
+    test("the flag round-trips back on through save and load", async () => {
+        const first = loadModuleWith(null);
+        first.mod.state.hideSpoofedSymbols = true;
+        await first.mod.saveState();
+        const persisted = first.set.mock.calls[0][0].autistmask;
+
+        const second = loadModuleWith(persisted);
+        await second.mod.loadState();
+        expect(second.mod.state.hideSpoofedSymbols).toBe(true);
+    });
+});

tests/transactions.test.js

@@ -78,6 +78,7 @@ const ORDINARY_PEER = "0x5aa0f9f1e0a1d0e0e5c1e7ce3b7dbbe9c19f0a11";
 
 // The documented default settings (README.md:810-814, state.js:24-27).
 const DEFAULT_FILTERS = {
+    hideSpoofedSymbols: true,
     hideLowHolderTokens: true,
     hideFraudContracts: true,
     hideDustTransactions: true,
@@ -329,44 +330,150 @@ describe("known-symbol spoof verification", () => {
         expect(result.newFraudContracts).toEqual([]);
     });
 
-    // Documents current behaviour, not desired behaviour: the spoof check
-    // compares tx.contractAddress against a lowercased known address with
-    // ===, so a caller passing a checksummed address for a genuine token has
-    // it treated as a spoof.  In the app this cannot happen because
-    // parseTokenTransfer lowercases, but the exported function is not
-    // defensive about it the way the blocklist check is.
-    test("current behaviour: a checksummed genuine contract is treated as a spoof", () => {
-        const genuineButChecksummed = tokenTx({
-            contractAddress: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
-        });
-        const result = filterTransactions([genuineButChecksummed], filters());
-        expect(result.transactions).toEqual([]);
+    // Regression guard (#179): EIP-55 mixed case is a checksum over the
+    // address, not part of its identity, so the contract comparison must be
+    // case-insensitive in both directions — a genuine token in any casing is
+    // genuine, and a spoof cannot escape detection by changing its casing.
+    test("a genuine contract in all-lowercase form is not a spoof", () => {
+        const tx = tokenTx({ contractAddress: USDC_CONTRACT });
+        expect(filterTransactions([tx], filters()).transactions).toEqual([tx]);
     });
 
-    // Documents current behaviour: README.md:810-814 says all four filters
-    // "default to on but can be individually disabled".  There is no setting
-    // for known-symbol verification, and filterTransactions applies it
-    // unconditionally, so it cannot be turned off.
-    test("current behaviour: spoof filtering cannot be disabled by any setting", () => {
-        const allFiltersOff = {
+    test("a genuine contract in EIP-55 checksummed form is not a spoof", () => {
+        const tx = tokenTx({
+            contractAddress: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
+        });
+        const result = filterTransactions([tx], filters());
+        expect(result.transactions).toEqual([tx]);
+        expect(result.newFraudContracts).toEqual([]);
+    });
+
+    test("a genuine contract in all-uppercase form is not a spoof", () => {
+        const tx = tokenTx({
+            contractAddress: "0X" + USDC_CONTRACT.slice(2).toUpperCase(),
+        });
+        const result = filterTransactions([tx], filters());
+        expect(result.transactions).toEqual([tx]);
+        expect(result.newFraudContracts).toEqual([]);
+    });
+
+    test("a genuinely different contract claiming USDC is still a spoof in any casing", () => {
+        const tx = tokenTx({
+            contractAddress: "0xD05339F9EA5AB9D9F03B9D57F671D2ABD1F55C82",
+        });
+        const result = filterTransactions([tx], filters());
+        expect(result.transactions).toEqual([]);
+        // The recorded fraud contract is normalised, so the persisted
+        // blocklist matches later transfers whatever casing they arrive in.
+        expect(result.newFraudContracts).toEqual([FAKE_ETH_CONTRACT]);
+    });
+
+    // Turning the other three filters off must not turn this one off: each
+    // filter is independent, and this is the one the README calls out as the
+    // defense against the fake "ETH" attack.
+    test("the check still runs when the other three filters are off", () => {
+        const result = filterTransactions(
+            [fakeEthTokenTransfer()],
+            filters({
                 hideLowHolderTokens: false,
                 hideFraudContracts: false,
                 hideDustTransactions: false,
                 dustThresholdGwei: 1,
-            fraudContracts: [],
-        };
-        const result = filterTransactions(
-            [fakeEthTokenTransfer()],
-            allFiltersOff,
+            }),
         );
         expect(result.transactions).toEqual([]);
         expect(result.newFraudContracts).toEqual([FAKE_ETH_CONTRACT]);
     });
 
-    test("current behaviour: spoof filtering also applies with no filters argument", () => {
+    test("spoof filtering also applies with no filters argument", () => {
         const result = filterTransactions([fakeEthTokenTransfer()]);
         expect(result.transactions).toEqual([]);
     });
+
+    // Fail-safe: unlike the other three flags, an absent hideSpoofedSymbols
+    // leaves the check ON.  A caller that forgets the key keeps the wallet's
+    // headline protection; only a user who deliberately switched the setting
+    // off sends an explicit false.
+    test("an absent hideSpoofedSymbols leaves the check on", () => {
+        const result = filterTransactions([fakeEthTokenTransfer()], {
+            fraudContracts: [],
+        });
+        expect(result.transactions).toEqual([]);
+    });
+
+    test("a truthy-but-not-true hideSpoofedSymbols leaves the check on", () => {
+        const result = filterTransactions(
+            [fakeEthTokenTransfer()],
+            filters({ hideSpoofedSymbols: undefined }),
+        );
+        expect(result.transactions).toEqual([]);
+    });
+});
+
+describe("disabling known-symbol spoof verification", () => {
+    test("the spoofed transfer is shown when hideSpoofedSymbols is false", () => {
+        const attack = fakeEthTokenTransfer();
+        const result = filterTransactions(
+            [attack],
+            filters({
+                hideSpoofedSymbols: false,
+                // The blocklist rule would otherwise hide the same row via a
+                // contract this pass had already learned.
+                hideFraudContracts: false,
+                hideLowHolderTokens: false,
+            }),
+        );
+        expect(result.transactions).toEqual([attack]);
+    });
+
+    // The blocklist is populated only by this check, so switching the check
+    // off stops the learning too.  Leaving learning on would make the setting
+    // a no-op: the contract it recorded would immediately hide the same row
+    // through the fraud-contract rule, which is on by default.
+    test("no fraud contract is learned when hideSpoofedSymbols is false", () => {
+        const result = filterTransactions(
+            [fakeEthTokenTransfer()],
+            filters({ hideSpoofedSymbols: false }),
+        );
+        expect(result.newFraudContracts).toEqual([]);
+    });
+
+    test("the setting off does not stop the other three rules", () => {
+        const dust = nativeDustTransfer();
+        const lowHolder = tokenTx({
+            symbol: NOVEL_SPAM_SYMBOL,
+            contractAddress: NOVEL_SPAM_CONTRACT,
+            holders: 0,
+        });
+        const result = filterTransactions(
+            [dust, lowHolder],
+            filters({ hideSpoofedSymbols: false }),
+        );
+        expect(result.transactions).toEqual([]);
+    });
+
+    // An already-persisted fraud contract keeps being filtered: the blocklist
+    // rule is a separate setting and is unaffected by this one.
+    test("an already-blocklisted contract is still hidden with the check off", () => {
+        const result = filterTransactions(
+            [fakeEthTokenTransfer()],
+            filters({
+                hideSpoofedSymbols: false,
+                fraudContracts: [FAKE_ETH_CONTRACT],
+            }),
+        );
+        expect(result.transactions).toEqual([]);
+        expect(result.newFraudContracts).toEqual([]);
+    });
+
+    test("a genuine transfer is unaffected by the setting either way", () => {
+        const tx = tokenTx();
+        expect(
+            filterTransactions([tx], filters({ hideSpoofedSymbols: false }))
+                .transactions,
+        ).toEqual([tx]);
+        expect(filterTransactions([tx], filters()).transactions).toEqual([tx]);
+    });
 });
 
 describe("low-holder token filtering (the 1,000-holder rule)", () => {
@@ -412,6 +519,21 @@ describe("low-holder token filtering (the 1,000-holder rule)", () => {
         expect(tx.holders).toBeNull();
         expect(filterTransactions([tx], filters()).transactions).toEqual([tx]);
     });
+
+    // Regression guard (#179): an unknown holder count on a real token — the
+    // explorer rate-limited the call, or a self-hosted instance omits the
+    // field — must not be read as zero holders.  Reading it that way hides a
+    // legitimate transfer from the user's history, the same over-filtering
+    // harm as the zero-threshold bug.  This pins the `tx.holders !== null`
+    // guard, which no fixture previously reached.
+    test("a token whose holder count is unknown is not filtered", () => {
+        const tx = tokenTx({
+            symbol: NOVEL_SPAM_SYMBOL,
+            contractAddress: NOVEL_SPAM_CONTRACT,
+            holders: null,
+        });
+        expect(filterTransactions([tx], filters()).transactions).toEqual([tx]);
+    });
 });
 
 describe("fraud contract blocklist", () => {
@@ -575,21 +697,56 @@ describe("dust threshold filtering", () => {
         expect(filterTransactions([tx], filters()).transactions).toEqual([tx]);
     });
 
-    // Documents current behaviour: the threshold is read as
-    // `filters.dustThresholdGwei || 100000`, so a user who sets the threshold
-    // to 0 (the natural way to ask for no dust filtering while leaving the
-    // toggle on) silently gets the 100,000 gwei default instead.
-    test("current behaviour: a threshold of 0 falls back to the 100,000 gwei default", () => {
-        const result = filterTransactions(
-            [dustOf(50)],
+    // Regression guard (#179): 0 is a real threshold meaning "hide nothing",
+    // not an absent one.  It used to be swallowed by `|| 100000`, so the one
+    // value a user would pick to see everything was the one that did not
+    // work.
+    test("a threshold of 0 hides nothing, leaving the toggle on", () => {
+        const dust = dustOf(50);
+        const zero = dustOf(0);
+        const opts = filters({ dustThresholdGwei: 0 });
+        expect(filterTransactions([dust], opts).transactions).toEqual([dust]);
+        expect(filterTransactions([zero], opts).transactions).toEqual([zero]);
+    });
+
+    test("a threshold of 0 agrees with clearing the hide-dust checkbox", () => {
+        const tx = nativeDustTransfer();
+        const thresholdZero = filterTransactions(
+            [tx],
             filters({ dustThresholdGwei: 0 }),
         );
-        expect(result.transactions).toEqual([]);
+        const toggleOff = filterTransactions(
+            [tx],
+            filters({ hideDustTransactions: false }),
+        );
+        expect(thresholdZero.transactions).toEqual([tx]);
+        expect(toggleOff.transactions).toEqual([tx]);
+    });
+
+    test("0, unset and a set threshold are three distinct behaviours", () => {
+        const tx = dustOf(50);
+        expect(
+            filterTransactions([tx], filters({ dustThresholdGwei: 0 }))
+                .transactions,
+        ).toEqual([tx]);
+        expect(
+            filterTransactions([tx], filters({ dustThresholdGwei: undefined }))
+                .transactions,
+        ).toEqual([]);
+        expect(
+            filterTransactions([tx], filters({ dustThresholdGwei: 40 }))
+                .transactions,
+        ).toEqual([tx]);
+        expect(
+            filterTransactions([tx], filters({ dustThresholdGwei: 60 }))
+                .transactions,
+        ).toEqual([]);
     });
 });
 
 describe("filter defaults promised by the README and Settings", () => {
-    test("all three toggles default to on and the threshold to 100,000 gwei", () => {
+    test("all four toggles default to on and the threshold to 100,000 gwei", () => {
+        expect(state.hideSpoofedSymbols).toBe(true);
         expect(state.hideLowHolderTokens).toBe(true);
         expect(state.hideFraudContracts).toBe(true);
         expect(state.hideDustTransactions).toBe(true);
@@ -600,10 +757,10 @@ describe("filter defaults promised by the README and Settings", () => {
         expect(state.fraudContracts).toEqual([]);
     });
 
-    // Documents current behaviour: filterTransactions itself defaults every
-    // optional filter to off.  The "default to on" promise is satisfied by
-    // the state defaults above, which every caller passes in; the pure
-    // function makes no assumption of its own.
+    // Documents current behaviour: filterTransactions defaults the other three
+    // optional filters to off.  Their "default to on" promise is satisfied by
+    // the state defaults above, which every caller passes in.  Spoof
+    // verification is the exception and stays on unless explicitly disabled.
     test("current behaviour: with no filters argument only spoof filtering runs", () => {
         const dust = nativeDustTransfer();
         const lowHolder = tokenTx({