Brand impersonation: Microsoft with low reputation links
Detects low reputation links with Microsoft specific indicators in the body.
Sublime rule (View on GitHub)
1name: "Brand impersonation: Microsoft with low reputation links"
2description: "Detects low reputation links with Microsoft specific indicators in the body."
3type: "rule"
4severity: "medium"
5source: |
6 type.inbound
7 and 0 < length(body.links) < 50
8 // suspicious link
9 and any(body.links,
10 (
11 .href_url.domain.root_domain not in $tranco_1m
12 or .href_url.domain.domain in $free_file_hosts
13 or .href_url.domain.root_domain in $free_file_hosts
14 or .href_url.domain.root_domain in $free_subdomain_hosts
15 or .href_url.domain.domain in $url_shorteners
16 or
17
18 // mass mailer link, masks the actual URL
19 .href_url.domain.root_domain in (
20 "hubspotlinks.com",
21 "mandrillapp.com",
22 "sendgrid.net",
23 "rs6.net"
24 )
25
26 // Google AMP redirect
27 or (
28 .href_url.domain.sld == "google"
29 and strings.starts_with(.href_url.path, "/amp/")
30 )
31
32 // Recipient email address in link
33 or any(body.links,
34 any(recipients.to,
35 strings.icontains(..href_url.url, .email.email)
36 and any(recipients.to, .email.domain.valid)
37 )
38 )
39 or .href_url.domain.root_domain == "beehiiv.com"
40 )
41
42 // exclude sources of potential FPs
43 and (
44 .href_url.domain.root_domain not in (
45 "svc.ms",
46 "sharepoint.com",
47 "1drv.ms",
48 "microsoft.com",
49 "aka.ms",
50 "msftauthimages.net",
51 "mimecastprotect.com",
52 "office.com",
53 "microsoftproject.com"
54 )
55 or any(body.links, .href_url.domain.domain in $free_file_hosts)
56 )
57 and .href_url.domain.root_domain not in $org_domains
58 and .href_url.domain.valid
59 )
60
61 // not a reply
62 and (
63 length(headers.references) == 0
64 or not any(headers.hops, any(.fields, strings.ilike(.name, "In-Reply-To")))
65 )
66
67 // Microsoft logo
68 and (
69 any(attachments,
70 .file_type in $file_types_images
71 and any(ml.logo_detect(.).brands, strings.starts_with(.name, "Microsoft"))
72 )
73 or strings.istarts_with(strings.replace_confusables(body.current_thread.text), "Microsoft ")
74 or regex.imatch(strings.replace_confusables(body.current_thread.text), '[\n\s]*[o0O]ff[il1]ce\b.*')
75 or any(ml.logo_detect(beta.message_screenshot()).brands,
76 strings.starts_with(.name, "Microsoft")
77 )
78 or (
79 regex.icontains(body.html.raw,
80 '<table[^>]*>\s*<tbody[^>]*>\s*<tr[^>]*>\s*(<td[^>]*bgcolor="#[0-9A-Fa-f]{6}"[^>]*>\s* \s*</td>\s*){2}\s*</tr>\s*<tr[^>]*>\s*(<td[^>]*bgcolor="#[0-9A-Fa-f]{6}"[^>]*>\s* \s*</td>\s*){2}'
81 )
82 or regex.icontains(body.html.raw,
83 '<td style="background:\s*rgb\(246,\s*93,\s*53\);\s*height:\d+px;">.*?<td style="background:\s*rgb\(129,\s*187,\s*5\);\s*height:\d+px;">.*?<td style="background:\s*rgb\(4,\s*165,\s*240\);\s*height:\d+px;">.*?<td style="background:\s*rgb\(255,\s*186,\s*7\);\s*height:\d+px;">'
84 )
85 or 4 of (
86 regex.icontains(body.html.raw,
87 '<td style="width:.\d.px;.height:.\d.px;.background-color:.rgb\(245, 189, 67\);">.{0,10}</td>'
88 ),
89 regex.icontains(body.html.raw,
90 '<td style="width:.\d.px;.height:.\d.px;.background-color:.rgb\(137, 184, 57\);">.{0,10}</td>'
91 ),
92 regex.icontains(body.html.raw,
93 '<td style="width:.\d.px;.height:.\d.px;.background-color:.rgb\(217, 83, 51\);">.{0,10}</td>'
94 ),
95 regex.icontains(body.html.raw,
96 '<td style="width:.\d.px;.height:.\d.px;.background-color:.rgb\(71, 160, 218\);">.{0,10}</td>'
97 )
98 )
99 )
100 or regex.icontains(body.html.raw,
101 '<table[^>]*>\s*<tbody[^>]*>\s*<tr[^>]*>\s*(<td[^>]*bgcolor="#[0-9A-Fa-f]{6}"[^>]*>\s* \s*</td>\s*){2}\s*</tr>\s*<tr[^>]*>\s*(<td[^>]*bgcolor="#[0-9A-Fa-f]{6}"[^>]*>\s* \s*</td>\s*){2}'
102 )
103 or 3 of (
104 regex.icontains(body.html.raw, '.password-expiration'),
105 regex.icontains(body.html.raw, 'color: #2672ec;'),
106 regex.icontains(body.html.raw, 'Microsoft')
107 )
108 or 4 of (
109 regex.icontains(body.html.raw, 'rgb\(246,\s?93,\s?53\)'),
110 regex.icontains(body.html.raw, 'rgb\(129,\s?187,\s?5\)'),
111 regex.icontains(body.html.raw, 'rgb\(4,\s?165,\s?240\)'),
112 regex.icontains(body.html.raw, 'rgb\(255,\s?186,\s?7\)'),
113 )
114 or 4 of (
115 regex.icontains(body.html.raw,
116 '(background-color:|background:|bgcolor=)(.)red'
117 ),
118 regex.icontains(body.html.raw, 'rgb\(19,\s?186,\s?132\)'),
119 regex.icontains(body.html.raw, 'rgb\(4,\s?166,\s?240\)'),
120 regex.icontains(body.html.raw, 'rgb\(255,\s?186,\s?8\)'),
121 )
122 or 4 of (
123 regex.icontains(body.html.raw, 'rgb\(245,\s?189,\s?67\)'),
124 regex.icontains(body.html.raw, 'rgb\(137,\s?184,\s?57\)'),
125 regex.icontains(body.html.raw, 'rgb\(217,\s?83,\s?51\)'),
126 regex.icontains(body.html.raw, 'rgb\(71,\s?160,\s?218\)')
127 )
128 or 4 of (
129 regex.icontains(body.html.raw, 'rgb\(73,\s?161,\s?232\)'),
130 regex.icontains(body.html.raw, 'rgb\(224,\s?92,\s?53\)'),
131 regex.icontains(body.html.raw, 'rgb\(139,\s?183,\s?55\)'),
132 regex.icontains(body.html.raw, 'rgb\(244,\s?188,\s?65\)')
133 )
134 or 4 of (
135 regex.icontains(body.html.raw, 'rgb\(213,\s?56,\s?62\)'),
136 regex.icontains(body.html.raw, 'rgb\(0,\s?114,\s?30\)'),
137 regex.icontains(body.html.raw, 'rgb\(0,\s?110,\s?173\)'),
138 regex.icontains(body.html.raw, 'rgb\(227,\s?209,\s?43\)'),
139 )
140 or 4 of (
141 regex.icontains(body.html.raw, 'rgb\(246,\s?93,\s?53\)'),
142 regex.icontains(body.html.raw, 'rgb\(129,\s?187,\s?5\)'),
143 regex.icontains(body.html.raw, 'rgb\(4,\s?165,\s?240\)'),
144 regex.icontains(body.html.raw, 'rgb\(255,\s?186,\s?7\)')
145 )
146 or 4 of (
147 regex.icontains(body.html.raw, 'rgb\(242,\s?80,\s?34\)'),
148 regex.icontains(body.html.raw, 'rgb\(127,\s?186,\s?0\)'),
149 regex.icontains(body.html.raw, 'rgb\(0,\s?164,\s?239\)'),
150 regex.icontains(body.html.raw, 'rgb\(255,\s?185,\s?0\)'),
151 )
152 or 4 of (
153 regex.icontains(body.html.raw, 'rgb\(243,\s?83,\s?37\)'),
154 regex.icontains(body.html.raw, 'rgb\(129,\s?188,\s?6\)'),
155 regex.icontains(body.html.raw, 'rgb\(5,\s?166,\s?240\)'),
156 regex.icontains(body.html.raw, 'rgb\(255,\s?186,\s?8\)')
157 )
158 or 4 of (
159 regex.icontains(body.html.raw, 'rgb\(243,\s?80,\s?34\)'),
160 regex.icontains(body.html.raw, 'rgb\(128,\s?187,\s?3\)'),
161 regex.icontains(body.html.raw, 'rgb\(3,\s?165,\s?240\)'),
162 regex.icontains(body.html.raw, 'rgb\(255,\s?185,\s?3\)')
163 )
164 or 4 of (
165 regex.icontains(body.html.raw,
166 '(background-color:|background:|bgcolor=)(.)?(#)?(FF1940|eb5024|F25022|FF1941|red)'
167 ),
168 regex.icontains(body.html.raw,
169 '(background-color:|background:|bgcolor=)(.)?(#)?(36ba57|3eb55d|7db606|7FBA00|36ba58|green)'
170 ),
171 regex.icontains(body.html.raw,
172 '(background-color:|background:|bgcolor=)(.)?#(04a1d6|04B5F0|05a1e8|00A4EF|01a4ef|04a5f0)'
173 ),
174 regex.icontains(body.html.raw,
175 '(background-color:|background:|bgcolor=)(.)?#(FFCA07|f7b408|FFB900|FFCA08|ffb901|ffba07)'
176 ),
177 )
178 or 4 of (
179 regex.icontains(body.html.raw,
180 '(background-color:|background:|bgcolor=)(.)?#(f65314|f65d35|49a1e8|E74F23|F35325)'
181 ),
182 regex.icontains(body.html.raw,
183 '(background-color:|background:|bgcolor=)(.)?#(7cbf42|81bb05|e05c35|7AB206|81BC06)'
184 ),
185 regex.icontains(body.html.raw,
186 '(background-color:|background:|bgcolor=)(.)?#(00a4ef|0078d7|8bb737|04a5f0|059EE4|05A6F0)'
187 ),
188 regex.icontains(body.html.raw,
189 '(background-color:|background:|bgcolor=)(.)?#(ffb900|ffba07|f4bc41|F2B108|FFBA08)'
190 ),
191 )
192 // fuzzy approach
193 or 4 of (
194 regex.icontains(body.html.raw,
195 'rgb\((2[1-4][0-9]|250),\s?(7[0-9]|8[0-9]|9[0-3]),\s?(3[0-9]|4[0-9]|5[0-3])\)'
196 ),
197 regex.icontains(body.html.raw,
198 'rgb\((12[0-9]|13[0-9]),\s?(18[0-9]|190),\s?([0-9]|10)\)'
199 ),
200 regex.icontains(body.html.raw,
201 'rgb\(([0-9]|1[0-5]),\s?(16[0-5]|166),\s?(23[0-9]|240)\)'
202 ),
203 regex.icontains(body.html.raw,
204 'rgb\((25[0-5]),\s?(18[5-9]|19[0-9]),\s?([0-9]|10)\)'
205 )
206 )
207 )
208
209 // suspicious content
210 and (
211 // current thread is empty, but an image attachment is branded as microsoft.
212 // common in image as content
213 (
214 body.current_thread.text == ""
215 and any(attachments,
216 .file_type in $file_types_images
217 and any(ml.logo_detect(.).brands,
218 strings.starts_with(.name, "Microsoft")
219 )
220 )
221 )
222 or (
223 strings.ilike(body.plain.raw,
224 "*password*",
225 "*document*",
226 "*voicemail*",
227 "*cache*",
228 "*fax*",
229 "*storage*",
230 "*quota*",
231 "*message*"
232 )
233 and strings.ilike(body.plain.raw,
234 "*terminated*",
235 "*review*",
236 "*expire*",
237 "*click*",
238 "*view*",
239 "*exceed*",
240 "*clear*",
241 "*only works*",
242 "*failed*",
243 "*deleted*",
244 "*revalidated*",
245 "*renewal*"
246 )
247 )
248
249 or (
250 any(attachments,
251 .file_type in $file_types_images
252 and any(file.explode(.),
253 strings.ilike(.scan.ocr.raw,
254 "*password*",
255 "*document*",
256 "*voicemail*",
257 "*cache*",
258 "*fax*",
259 "*storage*",
260 "*quota*",
261 "*messages*"
262 )
263 and strings.ilike(.scan.ocr.raw,
264 "*terminated*",
265 "*review*",
266 "*expire*",
267 "*click*",
268 "*view*",
269 "*exceed*",
270 "*clear*",
271 "*only works*",
272 "*failed*",
273 "*deleted*"
274 )
275 )
276 )
277 )
278 or (
279 any(file.explode(beta.message_screenshot()),
280 strings.ilike(.scan.ocr.raw,
281 "*password*",
282 "*document*",
283 "*voicemail*",
284 "*cache*",
285 "*fax*",
286 "*storage*",
287 "*quota*",
288 "*messages*"
289 )
290 and strings.ilike(.scan.ocr.raw,
291 "*terminated*",
292 "*review*",
293 "*expire*",
294 "*click*",
295 "*view*",
296 "*exceed*",
297 "*clear*",
298 "*only works*",
299 "*failed*",
300 "*deleted*",
301 "*revalidated*",
302 "*renewal*"
303 )
304 )
305 )
306 or (
307 any(ml.nlu_classifier(body.current_thread.text).intents,
308 .name == "cred_theft" and .confidence in~ ("medium", "high")
309 )
310 or any(attachments,
311 .file_type in $file_types_images
312 and any(file.explode(.),
313 any(ml.nlu_classifier(.scan.ocr.raw).intents,
314 .name == "cred_theft"
315 and .confidence in ("medium", "high")
316 )
317 )
318 )
319 )
320 )
321 and sender.email.domain.root_domain not in (
322 "bing.com",
323 "microsoft.com",
324 "microsoftonline.com",
325 "microsoftproject.com",
326 "microsoftstoreemail.com",
327 "microsoftsupport.com",
328 "microsoft365.com",
329 "office.com",
330 "office365.com",
331 "onedrive.com",
332 "sharepointonline.com",
333 "yammer.com",
334 )
335
336 // negate legitimate Office 365 bouncebacks
337 and not (
338 length(attachments) > 0
339 and all(attachments,
340 .content_type in ("message/delivery-status", "message/rfc822")
341 )
342 and (sender.email.local_part in ('postmaster', 'mailer-daemon'))
343 )
344
345 // negate Microsoft "welcome to the X group" notifications
346 and not (
347 headers.auth_summary.dmarc.pass
348 and length(attachments) == 6
349 and length(filter(attachments,
350 strings.istarts_with(.file_name, "GuestWelcomeEmail")
351 )
352 ) == 5
353 and length(filter(body.links,
354 (
355 .href_url.domain.domain not in (
356 "outlook.office365.com",
357 "aka.ms",
358 "go.microsoft.com"
359 )
360 )
361 and not .href_url.domain.domain == sender.email.domain.domain
362 )
363 ) == 0
364 and subject.subject == strings.replace_confusables(subject.subject)
365 )
366
367 // negate highly trusted sender domains unless they fail DMARC authentication
368 and (
369 (
370 sender.email.domain.root_domain in $high_trust_sender_root_domains
371 and not headers.auth_summary.dmarc.pass
372 )
373 or sender.email.domain.root_domain not in $high_trust_sender_root_domains
374 )
375 and (
376 not profile.by_sender().solicited
377 or (
378 profile.by_sender().any_messages_malicious_or_spam
379 and not profile.by_sender().any_false_positives
380 )
381 )
382 and not profile.by_sender().any_false_positives
383
384 // exclude marketing jargon from ms partners
385 and not regex.icontains(body.current_thread.text,
386 '(schedul(e|ing)|set up).{0,20}(call|meeting|demo|zoom|conversation|time|tool|discussion)|book.{0,10}(meeting|demo|call|slot|time)|connect.{0,12}(with me|phone|email)|my.{0,10}(calendar|cal)|reserve.{0,10}s[pl]ot|break the ice|want to know more?|miss your chance|if you no longer wish|if you no longer want|if you wish to opt out|low-code (development|approach|solution|journey|platform)|(?:invite|virtual).{0,30}(webinar|presentation)'
387 )
388attack_types:
389 - "Credential Phishing"
390tactics_and_techniques:
391 - "Free file host"
392 - "Image as content"
393 - "Impersonation: Brand"
394 - "Social engineering"
395detection_methods:
396 - "Computer Vision"
397 - "Content analysis"
398 - "File analysis"
399 - "Header analysis"
400 - "Natural Language Understanding"
401 - "Optical Character Recognition"
402 - "Sender analysis"
403 - "URL analysis"
404id: "b59201b6-f253-55a6-9c0a-e1500a32a751"