Malicious PDF — malware analysis report

Static analysis result for SHA-256 2644c8bdf0c0092a…

MALICIOUS

PDF

8.1 KB
MD5: ff6ac3984d2c2b77234c8c5e072e3c21 SHA-1: c99beb7d90c66a4351df004db606549a5addb334 SHA-256: 2644c8bdf0c0092a55b881400caf8df1671e5324c2bfa5a32c8c37aa3eaeef1f
166 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell

The PDF contains heavily obfuscated JavaScript, identified as a multi-stage dropper. The heuristics indicate that it decodes a payload from an annotation subject and uses incremental evaluation to build its execution methods. This dropper is designed to download and execute a second-stage payload, as evidenced by the ClamAV detection name 'Pdf.Exploit.Agent-36086'. The presence of multiple JavaScript streams and obfuscation techniques points to a sophisticated delivery mechanism.

Heuristics 7

  • ClamAV: Pdf.Exploit.Agent-36086 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Pdf.Exploit.Agent-36086
  • unescape() call high PDF_UNESCAPE
    unescape() found — often used to decode shellcode in PDF JS exploits (matched inside decoded stream)
  • Obfuscated multi-stage PDF JavaScript dropper high PDF_JS_OBFUSCATED_DROPPER
    PDF JavaScript shows 3 independent signals of exploit-kit-style multi-stage obfuscation: annot_subject_stage, incremental_eval_build, repeated_pluginschk. This is strongly consistent with pre-2011 Adobe Reader PDF droppers — OpenAction JS reads encoded data from annotation subjects, decodes it through one or more hex / base-N loops, and invokes eval indirectly (method name built one character at a time). The actual CVE is hidden in the final decoded layer and is not visible via static analysis.
  • JavaScript action low PDF_JAVASCRIPT
    PDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • Embedded JS stream low PDF_JS
    PDF references a /JS stream. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • syncAnnotScan annotation-staging primitive low PDF_FOXIT_SYNCANNOTSCAN
    PDF JavaScript calls syncAnnotScan() — a no-op annotation-enumeration primitive used by exploit-kit JavaScript to stage payload reads from annotation /Subject fields before eval(). Not a vulnerable sink itself; rarely seen in legitimate PDFs. (matched in decompressed stream)
  • Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj0006_000.js
f9b4659beaf681d266cfb5046d495e7b144d406eff72e71ecd4d1451ae25ca11
pdf-javascript-stream PDF /JS object 6 at offset 0x143 481 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 eval/decoder/string-building token(s).
legacy_pdfkit_stage_000.js
10acdd51e9d29eb45a0a78f5a902ab56efe7f30fcba11573b8f185298b58dea1
deobfuscated-js repeated-marker hex decoded JavaScript at offset 0x1B81 1632 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 eval/decoder/string-building token(s).
deobfuscated.js
4ae611106714edf2b8db4a695ef2e5a95f94e84edaa8d97793833c7db30499cc
deobfuscated-js PDF JavaScript deobfuscation pass 20435 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 4 eval/decoder/string-building token(s). Carved artifact contains 2 long base64-like blob(s).