sublimemediumRule

Link: Flagged bit.ly link

Shortened link is blocked or gated by bit.ly. Indicator of malicious email.

MITRE ATT&CK

T1566 T1566.001 T1566.002 T1598 T1036 T1027

defense-evasion

Detection Query

type.inbound
and any(body.links,
        // contains bit.ly link
        .href_url.domain.root_domain == "bit.ly"
        // link doesn't forward through
        and ml.link_analysis(.).effective_url.domain.domain == "bit.ly"
        // blocked or gated by bit.ly
        and strings.ilike(ml.link_analysis(.).final_dom.display_text,
                          "*link*blocked*",
                          "*flagged*by*"
        )
)

// negate highly trusted sender domains unless they fail DMARC authentication
and (
  (
    sender.email.domain.root_domain in $high_trust_sender_root_domains
    and not headers.auth_summary.dmarc.pass
  )
  or sender.email.domain.root_domain not in $high_trust_sender_root_domains
)
and (
  not profile.by_sender().solicited
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_messages_benign
  )
)
and not profile.by_sender().any_messages_benign

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Tags

Attack surface reduction

Raw Content

name: "Link: Flagged bit.ly link"
description: |
  Shortened link is blocked or gated by bit.ly. Indicator of malicious email.
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(body.links,
          // contains bit.ly link
          .href_url.domain.root_domain == "bit.ly"
          // link doesn't forward through
          and ml.link_analysis(.).effective_url.domain.domain == "bit.ly"
          // blocked or gated by bit.ly
          and strings.ilike(ml.link_analysis(.).final_dom.display_text,
                            "*link*blocked*",
                            "*flagged*by*"
          )
  )

  // negate highly trusted sender domains unless they fail DMARC authentication
  and (
    (
      sender.email.domain.root_domain in $high_trust_sender_root_domains
      and not headers.auth_summary.dmarc.pass
    )
    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
  )
  and (
    not profile.by_sender().solicited
    or (
      profile.by_sender().any_messages_malicious_or_spam
      and not profile.by_sender().any_messages_benign
    )
  )
  and not profile.by_sender().any_messages_benign
tags:
  - "Attack surface reduction"
attack_types:
  - "Credential Phishing"
tactics_and_techniques:
  - "Evasion"
detection_methods:
  - "URL analysis"
id: "1528eb6c-22fa-5879-b48c-53ee466fde23"