Formbook PDF malware analysis — malicious · 5e303fd9317236b5

MALICIOUS

PDF

195.6 KB First seen: 2022-02-24

MD5: 2375b40431bc19d172e4802dfb6187ed SHA-1: c59b3c5a107f76a5d7de0a482c48f32c1778b4cd SHA-256: 5e303fd9317236b55429aedd5c7aa133f3ea9dd2a50402930c50c5fbcc6e27e6

238 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK

T1566.001 Spearphishing Attachment T1059.007 JavaScript T1203 Exploitation for Client Execution

The PDF contains JavaScript that is configured to launch an embedded file upon opening, a common dropper technique. ClamAV and ML classifiers identify this as a Formbook downloader. The embedded file itself was also detected by ClamAV as a Formbook variant.

Machine Learning

Nyx PDF Classifier malicious score 0.9776

Heuristics 8

exportDataObject + nLaunch — embedded-file launch-on-open dropper critical PDF_JS_EXPORT_LAUNCH_DROPPER

PDF JavaScript calls exportDataObject() with nLaunch set, which extracts the document's embedded file and launches it in its default application. This is a launch-on-open dropper: the embedded file is the payload. No benign workflow auto-launches an extracted PDF attachment. (matched in decompressed stream)
ClamAV: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0
ClamAV detection on extracted artifact critical EXTRACTED_FILE_CLAMAV

ClamAV flagged at least one file extracted from inside this sample. Even when the wrapping document carries no AV detection of its own, a hit on the carved artifact is a strong indicator the sample is a delivery vehicle.
Embedded file low PDF_EMBEDDED

PDF embeds a file attachment — could carry an executable or another weaponised document as a nested payload
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. (matched inside decoded stream)
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. (matched inside decoded stream)
PDF paints image(s) but contains no text operators info PDF_IMAGE_ONLY_LURE

PDF has 2 image XObject(s) and the content stream contains no text-emitting operators (BT/ET, Tj, TJ, ', ") in either raw bytes or decompressed streams — this is the screenshot-as-PDF pattern used to bypass text-based scanners and to deliver instructions purely through rendered pixels. It is informational unless paired with invisible links or risky URI context.
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.

Filename	Kind	Source	Size
`embedded_file_obj0022.bin` `c2ea4fd93ebb20f04633380d4a66626376b8041892a456f0e53c7e6d4c7478d1`	pdf-embedded-file	PDF EmbeddedFile object 22 at offset 0x3B0F	190632 bytes
Detection ClamAV: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0 Obfuscation or payload: likely Carved artifact entropy is 7.96, consistent with packed or encrypted content.
`stream_006_off00030afc.bin` `1397e90565ca2158571ad3c29ccfad769ab2ef89bd9d64c6811f7ae0187c4b10`	decompressed-pdf-stream	PDF FlateDecoded stream at offset 0x30AFC	929 bytes

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