sublimehighRule

Adobe branded PDF file linking to a password-protected file from untrusted sender

Detects pdf files with links to a remotely hosted password-protected file. This is a common technique abused by Phishing actors as well as Malware actors (IcedID, Remcos, Async Rat)

MITRE ATT&CK

T1566.001 T1204.002 T1486 T1027 T1573 T1036 T1566.002 T1598.003

defense-evasioninitial-access

Detection Query

type.inbound
and any(attachments,
        .file_extension == "pdf"
        and any(file.explode(.),
                any(ml.nlu_classifier(.scan.ocr.raw).intents,
                    .name == "cred_theft" and .confidence == "high"
                )
                and strings.icontains(.scan.ocr.raw, "password-protected")
                and any(ml.nlu_classifier(.scan.ocr.raw).entities,
                        .name == "org" and .text == "Adobe"
                )
        )
)
and (
  profile.by_sender().prevalence in ("new", "outlier")
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_messages_benign
  )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Raw Content

name: "Adobe branded PDF file linking to a password-protected file from untrusted sender"
description: |
  Detects pdf files with links to a remotely hosted password-protected file. This is a common technique
  abused by Phishing actors as well as Malware actors (IcedID, Remcos, Async Rat)
type: "rule"
severity: "high"
source: |
  type.inbound
  and any(attachments,
          .file_extension == "pdf"
          and any(file.explode(.),
                  any(ml.nlu_classifier(.scan.ocr.raw).intents,
                      .name == "cred_theft" and .confidence == "high"
                  )
                  and strings.icontains(.scan.ocr.raw, "password-protected")
                  and any(ml.nlu_classifier(.scan.ocr.raw).entities,
                          .name == "org" and .text == "Adobe"
                  )
          )
  )
  and (
    profile.by_sender().prevalence in ("new", "outlier")
    or (
      profile.by_sender().any_messages_malicious_or_spam
      and not profile.by_sender().any_messages_benign
    )
  )
attack_types:
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Encryption"
  - "Evasion"
  - "Impersonation: Brand"
  - "PDF"
detection_methods:
  - "Archive analysis"
  - "File analysis"
  - "Natural Language Understanding"
  - "Optical Character Recognition"
  - "Sender analysis"
id: "5ea75469-58e8-561e-9a19-24da14a946b7"