Detection rules › Sublime MQL

Link to auto-downloaded file with Adobe branding

Severity
high
Type
rule
Source
github.com/sublime-security/sublime-rules

A link in the body of the email downloads a file from a site that uses Adobe branding as employed by threat actors, such as Qakbot.

Threat classification

Sublime's own taxonomy (not MITRE ATT&CK).

CategoryValues
Attack typesMalware/Ransomware
Tactics and techniquesImpersonation: Brand, Social engineering

Event coverage

Message attribute
body
type

Rule body MQL

type.inbound
and any(body.links,
        // There are files downloaded
        length(ml.link_analysis(.).files_downloaded) > 0
        and 

        // Adobe branding
        ml.link_analysis(.).credphish.brand.name == "Adobe"
        and ml.link_analysis(.).credphish.brand.confidence == "high"
        and 

        // Qakbot text for user coercion
        any(file.explode(ml.link_analysis(.).screenshot),
            all(["the file is not displayed correctly", "document password"],
                strings.icontains(..scan.ocr.raw, .)
            )
        )
)
and (
  not profile.by_sender().solicited
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_messages_benign
  )
)

Detection logic

Scope: inbound message.

A link in the body of the email downloads a file from a site that uses Adobe branding as employed by threat actors, such as Qakbot.

  1. inbound message
  2. any of body.links where all hold:
    • length(ml.link_analysis(.).files_downloaded) > 0
    • ml.link_analysis(.).credphish.brand.name is 'Adobe'
    • ml.link_analysis(.).credphish.brand.confidence is 'high'
    • any of file.explode(...) where:
      • all of ['the file is not displayed correctly', 'document password'] where:
        • strings.icontains(.scan.ocr.raw)
  3. any of:
    • not:
      • profile.by_sender().solicited
    • all of:
      • profile.by_sender().any_messages_malicious_or_spam
      • not:
        • profile.by_sender().any_messages_benign

Inspects: body.links, type.inbound. Sensors: file.explode, ml.link_analysis, profile.by_sender, strings.icontains.