PDF malware analysis — malicious · 4a936365e26be089

MALICIOUS

PDF

23.5 KB

MD5: fb801653825de2a0db5369e83c36f4d4 SHA-1: a0b67082e8946b3e5302f19aa708dac44b385201 SHA-256: 4a936365e26be089bd87859eb3f480f426632e22fd6c7fa17bb0b65c5ac93a12

164 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File T1566.001 Spearphishing Attachment T1140 Deobfuscate or Obfuscate Malicious Code

The PDF file contains obfuscated JavaScript, indicated by the use of eval(), unescape(), and String.fromCharCode(). The ML classifier strongly flags this PDF as malicious. The embedded JavaScript file, 'javascript_obj111611_000.js', is the primary artifact, and its presence suggests the PDF is designed to exploit vulnerabilities and execute malicious code, likely downloading a second-stage payload. The confidence is slightly reduced due to the lack of specific IOCs like URLs or hashes within the provided evidence.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 8

eval() call high PDF_EVAL

eval() found — commonly used for obfuscated exploit execution (matched inside decoded stream)
unescape() call high PDF_UNESCAPE

unescape() found — often used to decode shellcode in PDF JS exploits (matched inside decoded stream)
ASCIIHexDecode filter (with exploit indicators) medium PDF_FILTER_HEX

Hex-encoding filter present alongside exploit delivery indicators — often used to hide payload or shellcode bytes
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.
String.fromCharCode low PDF_FROMCHARCODE

String.fromCharCode found — used to construct payload strings dynamically. Common in benign JavaScript libraries for codepoint manipulation, so this alone is informational; weaponised use is also caught by the dedicated fromCharCode-stage and exploit-shape rules. (matched inside decoded stream)
ASCII85Decode filter (with exploit indicators) low PDF_FILTER_85

ASCII85 encoding filter present alongside exploit delivery indicators — uncommon outside of obfuscation
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 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj111611_000.js` `458486efaac72fcc281d53fcd971a3a09241fcc29a48004db3c406643a4a2a8d`	pdf-javascript-stream	PDF /JS object 111611 at offset 0x5BCD	246 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 3 eval/decoder/string-building token(s).

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