Request for Quote or Purchase (RFQ|RFP) with suspicious sender or recipient pattern
RFQ/RFP scams involve fraudulent emails posing as legitimate requests for quotations or purchases, often sent by scammers impersonating reputable organizations. These scams aim to deceive recipients into providing sensitive information or conducting unauthorized transactions, often leading to financial loss, or data leakage.
Sublime rule (View on GitHub)
1name: "Request for Quote or Purchase (RFQ|RFP) with suspicious sender or recipient pattern"
2description: |
3 RFQ/RFP scams involve fraudulent emails posing as legitimate requests for quotations or purchases, often sent by scammers impersonating reputable organizations.
4 These scams aim to deceive recipients into providing sensitive information or conducting unauthorized transactions, often leading to financial loss, or data leakage.
5type: "rule"
6severity: "medium"
7source: |
8 type.inbound
9 and (
10 (
11 (
12 length(recipients.to) == 0
13 or all(recipients.to,
14 .display_name in (
15 "Undisclosed recipients",
16 "undisclosed-recipients"
17 )
18 )
19 )
20 and length(recipients.cc) == 0
21 )
22 or (
23 sender.email.domain.root_domain in $free_email_providers
24 and any(headers.reply_to, .email.email != sender.email.email)
25 and any(headers.reply_to, .email.email not in $recipient_emails)
26 )
27 or (
28 length(headers.reply_to) > 0
29 and all(headers.reply_to,
30 .email.domain.root_domain != sender.email.domain.root_domain
31 and not .email.domain.root_domain in $org_domains
32 )
33 )
34 or (
35 length(recipients.to) == 1
36 and all(recipients.to, .email.email == sender.email.email)
37 and (length(recipients.cc) > 0 or length(recipients.bcc) > 0)
38 )
39 or (
40 length(recipients.to) == 0
41 and length(recipients.cc) == 1
42 and sender.email.email == recipients.cc[0].email.email
43 )
44 or (
45 length(recipients.to) == 1
46 and length(recipients.cc) == 0
47 and sender.email.email == recipients.to[0].email.email
48 )
49 )
50 and (
51 // Group the keyword patterns that specifically indicate RFQ/RFP
52 (
53 (
54 // RFQ/RFP specific language patterns
55 regex.icontains(body.current_thread.text,
56 '(discuss.{0,15}purchas(e|ing))'
57 )
58 or regex.icontains(body.current_thread.text,
59 '(sign(ed?)|view).{0,10}(purchase order)|Request for (a Quot(e|ation)|Proposal)'
60 )
61 or regex.icontains(body.current_thread.text,
62 '(please|kindly).{0,30}(?:proposal|quot(e|ation))'
63 )
64 or regex.icontains(subject.subject,
65 '(request for (purchase|quot(e|ation))|\bRFQ\b|\bRFP\b|bid invit(e|ation))'
66 )
67 or any(attachments,
68 regex.icontains(.file_name, "(purchase.?order|Quot(e|ation))")
69 )
70 or any(ml.nlu_classifier(body.current_thread.text).tags,
71 .name == "purchase_order" and .confidence == "high"
72 )
73 or any(ml.nlu_classifier(body.current_thread.text).entities,
74 .name == "financial" and regex.imatch(.text, "rfp|rfq")
75 )
76 or any(ml.nlu_classifier(body.current_thread.text).entities,
77 .name == "request" and strings.icontains(.text, 'submit bid')
78 )
79 )
80 // Required: at least one RFQ/RFP keyword pattern
81
82 // Optional: at least one additional indicator (can be another keyword pattern or a non-keyword indicator)
83 and (
84 2 of (
85 // RFQ/RFP keyword patterns (same as above)
86 regex.icontains(body.current_thread.text,
87 '(discuss.{0,15}purchas(e|ing))'
88 ),
89 regex.icontains(body.current_thread.text,
90 '(sign(ed?)|view).{0,10}(purchase order)|Request for a Quot(e|ation)'
91 ),
92 regex.icontains(body.current_thread.text,
93 '(please|kindly).{0,30}(?:proposal|quot(e|ation))'
94 ),
95 regex.icontains(body.current_thread.text,
96 '(?:invitation|intent) to bid'
97 ),
98 regex.icontains(subject.subject,
99 '(request for (purchase|quot(e|ation))|\bRFQ\b|\bRFP\b|bid invit(e|ation))'
100 ),
101 any(attachments,
102 regex.icontains(.file_name, "(purchase.?order|Quot(e|ation))")
103 ),
104 any(ml.nlu_classifier(body.current_thread.text).tags,
105 .name == "purchase_order" and .confidence == "high"
106 ),
107 any(ml.nlu_classifier(body.current_thread.text).entities,
108 .name == "financial" and regex.imatch(.text, "rfp|rfq")
109 ),
110
111 // Non-keyword indicators
112 (
113 any(ml.nlu_classifier(body.current_thread.text).entities,
114 .name == "request"
115 )
116 and any(ml.nlu_classifier(body.current_thread.text).entities,
117 .name == "urgency"
118 )
119 and not any(ml.nlu_classifier(body.current_thread.text).topics,
120 .name == "Advertising and Promotions"
121 and .confidence == "high"
122 )
123 ),
124 (
125 0 < length(filter(body.links,
126 (
127 .href_url.domain.domain in $free_subdomain_hosts
128 or .href_url.domain.domain in $free_file_hosts
129 or network.whois(.href_url.domain).days_old < 30
130 )
131 and (
132 regex.match(.display_text, '[A-Z ]+')
133 or any(ml.nlu_classifier(.display_text).entities,
134 .name in ("request", "urgency")
135 )
136 or any(ml.nlu_classifier(.display_text).intents,
137 .name in ("cred_theft")
138 )
139 )
140 )
141 ) < 3
142 ),
143 // mentions an attachment that does not exist
144 (
145 length(attachments) == 0
146 and strings.icontains(body.current_thread.text, "attached")
147 ),
148 any(body.current_thread.links, regex.icontains(.href_url.url, 'RFP'))
149 )
150 )
151 )
152 or (
153 length(attachments) == 1
154 and length(body.current_thread.text) < 100
155 and all(attachments,
156 .file_type in $file_types_images
157 and any(file.explode(.),
158 2 of (
159 regex.icontains(.scan.ocr.raw,
160 '(discuss.{0,15}purchas(e|ing))'
161 ),
162 regex.icontains(.scan.ocr.raw,
163 '(sign(ed?)|view).{0,10}(purchase order)|Request for a Quot(e|ation)'
164 ),
165 regex.icontains(.scan.ocr.raw,
166 '(please|kindly).{0,30}quote'
167 ),
168 (
169 any(ml.nlu_classifier(.scan.ocr.raw).entities,
170 .name == "request"
171 )
172 and any(ml.nlu_classifier(.scan.ocr.raw).entities,
173 .name == "urgency"
174 )
175 ),
176 any(ml.nlu_classifier(.scan.ocr.raw).tags,
177 .name == "purchase_order" and .confidence == "high"
178 ),
179 any(ml.nlu_classifier(.scan.ocr.raw).entities,
180 .name == "financial"
181 and regex.imatch(.text, "rfp|rfq")
182 ),
183 )
184 )
185 )
186 )
187 // fake PDF file icon used as a link lure with bid solicitation language
188 or (
189 regex.icontains(subject.subject, 'project\s+summary')
190 and any(html.xpath(body.html, '//div[.//img[contains(@src,"pdf")]]//a').nodes,
191 regex.icontains(.display_text, 'project\s+summary')
192 )
193 and regex.icontains(body.current_thread.text,
194 '(put a bid|\bbid\s+(for|on)\b|submit.{1,20}(bid|quot(e|ation))|request for (purchase|quot(e|ation))|\bRFQ\b|\bRFP\b|project\s+summary)'
195 )
196 )
197 )
198 // wetransfer includes user specific reply-to's & link display text which triggers NLU logic further within the rule
199 and not (
200 sender.email.domain.root_domain == "wetransfer.com"
201 and coalesce(headers.auth_summary.dmarc.pass, false)
202 )
203
204 // negate highly trusted sender domains unless they fail DMARC authentication
205 and (
206 (
207 sender.email.domain.root_domain in $high_trust_sender_root_domains
208 and not headers.auth_summary.dmarc.pass
209 )
210 or sender.email.domain.root_domain not in $high_trust_sender_root_domains
211 )
212 and (
213 (
214 (
215 not profile.by_sender().solicited
216 or profile.by_sender().days_since.last_contact > 30
217 )
218 and not profile.by_sender().any_messages_benign
219 )
220 // sender address listed as a recipient
221 or (
222 length(recipients.to) == 1
223 and sender.email.email in map(recipients.to, .email.email)
224 )
225 )
226attack_types:
227 - "BEC/Fraud"
228tactics_and_techniques:
229 - "Evasion"
230 - "Free email provider"
231detection_methods:
232 - "Content analysis"
233 - "Natural Language Understanding"
234 - "URL analysis"
235id: "2ac0d329-c1fb-5c87-98dd-ea3e5b85377a"