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|preferred).{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|preferred).{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 any(attachments,
111 any(file.explode(.),
112 any(ml.nlu_classifier(.scan.ocr.raw).entities,
113 .name == "request"
114 and regex.imatch(.text, "view (?:rfp|rfq)")
115 )
116 )
117 ),
118
119 // Non-keyword indicators
120 (
121 any(ml.nlu_classifier(body.current_thread.text).entities,
122 .name == "request"
123 )
124 and any(ml.nlu_classifier(body.current_thread.text).entities,
125 .name == "urgency"
126 )
127 and not any(ml.nlu_classifier(body.current_thread.text).topics,
128 .name == "Advertising and Promotions"
129 and .confidence == "high"
130 )
131 ),
132 (
133 0 < length(filter(body.links,
134 (
135 .href_url.domain.domain in $free_subdomain_hosts
136 or .href_url.domain.domain in $free_file_hosts
137 or network.whois(.href_url.domain).days_old < 30
138 )
139 and (
140 regex.match(.display_text, '[A-Z ]+')
141 or any(ml.nlu_classifier(.display_text).entities,
142 .name in ("request", "urgency")
143 )
144 or any(ml.nlu_classifier(.display_text).intents,
145 .name in ("cred_theft")
146 )
147 )
148 )
149 ) < 3
150 ),
151 // mentions an attachment that does not exist
152 (
153 length(attachments) == 0
154 and strings.icontains(body.current_thread.text, "attached")
155 ),
156 any(body.current_thread.links, regex.icontains(.href_url.url, 'RFP'))
157 )
158 )
159 )
160 or (
161 length(attachments) == 1
162 and length(body.current_thread.text) < 100
163 and all(attachments,
164 .file_type in $file_types_images
165 and any(file.explode(.),
166 2 of (
167 regex.icontains(.scan.ocr.raw,
168 '(discuss.{0,15}purchas(e|ing))'
169 ),
170 regex.icontains(.scan.ocr.raw,
171 '(sign(ed?)|view).{0,10}(purchase order)|Request for a Quot(e|ation)'
172 ),
173 regex.icontains(.scan.ocr.raw,
174 '(please|kindly).{0,30}quote'
175 ),
176 (
177 any(ml.nlu_classifier(.scan.ocr.raw).entities,
178 .name == "request"
179 )
180 and any(ml.nlu_classifier(.scan.ocr.raw).entities,
181 .name == "urgency"
182 )
183 ),
184 any(ml.nlu_classifier(.scan.ocr.raw).tags,
185 .name == "purchase_order" and .confidence == "high"
186 ),
187 any(ml.nlu_classifier(.scan.ocr.raw).entities,
188 .name == "financial"
189 and regex.imatch(.text, "rfp|rfq")
190 ),
191 )
192 )
193 )
194 )
195 // fake PDF file icon used as a link lure with bid solicitation language
196 or (
197 regex.icontains(subject.subject, 'project\s+summary')
198 and any(html.xpath(body.html, '//div[.//img[contains(@src,"pdf")]]//a').nodes,
199 regex.icontains(.display_text, 'project\s+summary')
200 )
201 and regex.icontains(body.current_thread.text,
202 '(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)'
203 )
204 )
205 )
206 // wetransfer includes user specific reply-to's & link display text which triggers NLU logic further within the rule
207 and not (
208 sender.email.domain.root_domain == "wetransfer.com"
209 and coalesce(headers.auth_summary.dmarc.pass, false)
210 )
211
212 // negate highly trusted sender domains unless they fail DMARC authentication
213 and (
214 (
215 sender.email.domain.root_domain in $high_trust_sender_root_domains
216 and not headers.auth_summary.dmarc.pass
217 )
218 or sender.email.domain.root_domain not in $high_trust_sender_root_domains
219 )
220 and (
221 (
222 (
223 not profile.by_sender().solicited
224 or profile.by_sender().days_since.last_contact > 30
225 )
226 and not profile.by_sender().any_messages_benign
227 )
228 // sender address listed as a recipient
229 or (
230 length(recipients.to) == 1
231 and sender.email.email in map(recipients.to, .email.email)
232 )
233 )
234attack_types:
235 - "BEC/Fraud"
236tactics_and_techniques:
237 - "Evasion"
238 - "Free email provider"
239detection_methods:
240 - "Content analysis"
241 - "Natural Language Understanding"
242 - "URL analysis"
243id: "2ac0d329-c1fb-5c87-98dd-ea3e5b85377a"