diff --git a/frontend/index.html b/frontend/index.html
index 798da0e..90d12d6 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -6672,6 +6672,13 @@ const PROFILER_IGNORE_FILES = [
 	{ fid: '6F43', name: 'EF.SMSS' },
 ];
 
+// Files where contents are captured as a mask matching only the first 4 bytes
+// (the rest are '?' wildcards). Keyed by FID; display name is the pySim name.
+const PROFILER_MASK_PREFIX4_FIDS = {
+	'6F07': 'EF.IMSI',
+	'2FE2': 'EF.ICCID',
+};
+
 function profilerLoad() {
 	try {
 		const d = localStorage.getItem('otaman_profiles');
@@ -6717,6 +6724,13 @@ function profilerMatchMin(mode, expected, actual) {
 	return profilerMatch(mode, e.slice(0, n), a.slice(0, n));
 }
 
+// Keep the first 4 bytes (8 hex chars) exact and mask the rest with '?'.
+function profilerMaskPrefix4(hex) {
+	const h = profilerNormHex(hex);
+	if (h.length <= 8) return h;
+	return h.slice(0, 8) + '?'.repeat(h.length - 8);
+}
+
 function profilerValidateProfile(obj) {
 	if (!obj || typeof obj !== 'object') return 'Not an object';
 	if (!obj.name) return 'Missing name';
@@ -6896,7 +6910,11 @@ async function profilerBuildFileRule(path, c, ignoreFids) {
 					records: rd.records.map(r => ({ num: r.num, data: r.data })),
 				};
 			} else if (rd.data) {
-				rule.content = { mode: 'exact', kind: 'transparent', expected: rd.data };
+				if (PROFILER_MASK_PREFIX4_FIDS[fid]) {
+					rule.content = { mode: 'mask', kind: 'transparent', expected: profilerMaskPrefix4(rd.data) };
+				} else {
+					rule.content = { mode: 'exact', kind: 'transparent', expected: rd.data };
+				}
 			}
 		}
 	} catch (e) {}
diff --git a/frontend/sw.js b/frontend/sw.js
index 764b916..a87b9ca 100644
--- a/frontend/sw.js
+++ b/frontend/sw.js
@@ -1,4 +1,4 @@
-const CACHE = 'otaman-v43';
+const CACHE = 'otaman-v44';
 const URLS = [
   'index.html',
   'help.html',
diff --git a/frontend/tests/profiler.test.js b/frontend/tests/profiler.test.js
index 3dc7eda..75f63f7 100644
--- a/frontend/tests/profiler.test.js
+++ b/frontend/tests/profiler.test.js
@@ -21,7 +21,7 @@ function extractFunc(src, name) {
 	return src.slice(m.index, i + 1);
 }
 
-const FNS = ['profilerNormHex', 'profilerMatch', 'profilerMatchMin', 'profilerValidateProfile'];
+const FNS = ['profilerNormHex', 'profilerMatch', 'profilerMatchMin', 'profilerMaskPrefix4', 'profilerValidateProfile'];
 let code = '';
 for (const f of FNS) code += extractFunc(html, f) + '\n';
 eval(code);
@@ -68,6 +68,12 @@ test('profilerMatchMin compares the shorter overlapping portion', () => {
 	assert.ok(!profilerMatchMin('mask', '08?91?AA', '091110'));
 });
 
+test('profilerMaskPrefix4 keeps first 4 bytes and masks the rest', () => {
+	assert.strictEqual(profilerMaskPrefix4('082905911234567890'), '08290591??????????');
+	assert.strictEqual(profilerMaskPrefix4('08290591'), '08290591');
+	assert.strictEqual(profilerMaskPrefix4('1234'), '1234');
+});
+
 test('profile validation', () => {
 	assert.strictEqual(profilerValidateProfile(null), 'Not an object');
 	assert.strictEqual(profilerValidateProfile({ name: 'x' }), 'Missing rules array');