High Severity

Attachment: PDF with EOF MD5 hash marker

Labels

Credential Phishing
Malware/Ransomware
PDF
Evasion
File analysis
YARA

Description

Detects inbound messages containing a PDF attachment whose contents match a YARA signature identifying an MD5 hash appended near the end of file. This technique is commonly used to make each generated PDF unique, helping evade hash-based detection systems.

References

No references.

Sublime Security
Created Sep 10th, 2026 • Last updated Sep 10th, 2026
Feed Source
Sublime Core Feed
Source
GitHub
type.inbound
and any(filter(attachments, .file_type == "pdf"),
        any(file.explode(.),
            any(.scan.yara.matches, .name in ("pdf_eof_md5_hash"))
        )
)
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