RTF malware analysis — malicious · f138baa6bbf1d8a6

MALICIOUS

RTF

6.84 MB First seen: 2019-11-20

MD5: b8f612d289b9dc44404dfd6e06ef511e SHA-1: 13b7c17fa90b4ad2f86e9aab28f29602018755dc SHA-256: f138baa6bbf1d8a6b489bca3aa0308e08b1003e2f4a3be664b16e9dc8255bb1d

262 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF document contains an embedded OLE object related to Equation Editor, specifically triggering CVE-2017-11882. This vulnerability is known to be used to execute arbitrary code. The presence of a large, high-entropy decoded object suggests it contains a second-stage payload, likely a PE file, which is then executed on the victim's machine.

Heuristics 7

Decoded Equation Editor payload + PE critical CVE likely RTF_EQUATION_EDITOR

RTF decodes to an Equation Editor ProgID adjacent to OLE activation and the same decoded object stream contains embedded PE bytes. This matches the Equation Editor exploit surface used by CVE-2017-11882 / CVE-2018-0802 documents, while requiring payload evidence to avoid flagging benign Equation references.
Equation Editor OLE1 native payload — CVE-2017-11882 related critical CVE related CVE_2017_11882_RELATED

RTF decodes to an OLE1 Equation.3 embedded object whose native data is large and payload-like, and \objupdate requests automatic activation. This is the delivery shape used by Equation Editor RCE documents such as CVE-2017-11882/CVE-2018-0802, but the malformed MTEF record needed for exact attribution was not recovered.
Automatically linked OLE object high RTF_OBJAUTLINK

RTF contains \objautlink — an automatically linked OLE object surface that can be updated or activated when Word opens the document.
\objupdate forces OLE activation high RTF_OBJUPDATE

RTF contains \objupdate — forces automatic OLE object instantiation when the document is opened, bypassing user interaction. Almost exclusively seen in Equation Editor exploit documents.
Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX

RTF contains ~7172KB of hex-encoded data inside \objdata sections — may hide a payload
OLE object data medium RTF_OBJDATA

RTF contains 1 \objdata section(s) — embedded OLE objects
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
`objdata_00_off00000070.bin`	rtf-objdata-decoded	RTF \objdata at offset 0x70	3586087 bytes
SHA-256: `59849d692c9af2cbe128b6fc25bec53eb72df2497ed4db32f568a1630272afbf`
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.99, consistent with packed or encrypted content.

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