RTF / .DOC malware analysis — malicious · f1c2be9c2b947f40

MALICIOUS

RTF / .DOC

1.72 MB First seen: 2022-03-02

MD5: dc721d8bf9cdcc60df5c3a9abb8425bd SHA-1: 2bd495464cd6dbdc3ed617c3709b405d9c9f5e5e SHA-256: f1c2be9c2b947f40bd03a0272d90734455c4622fb914fdf341e9ba0eb3e0bbbe

220 Risk Score

Malware Insights

MITRE ATT&CK

T1204.002 Malicious File Execution: User Execution: Malicious File T1566.001 Phishing: Spearphishing Attachment

The file is an RTF document containing an embedded OLE object that exploits the CVE-2017-11882 vulnerability in Microsoft Equation Editor. The presence of `RTF_EQUATION_EDITOR` and `CVE_2017_11882_RELATED` heuristics strongly indicates this exploit. The `RTF_OBJDATA` and `RTF_EXCESSIVE_HEX` heuristics suggest that a payload is hidden within the OLE object data, which is likely executed upon activation due to `RTF_OBJUPDATE`. The document body is heavily obfuscated and does not provide direct clues to the payload's intent, but the exploit itself is a common delivery mechanism for further malicious activity.

Heuristics 5

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.
Split hex Equation Editor ProgID + OLE object critical RTF_EQUATION_EDITOR

RTF embeds the Equation.3 ProgID as hex bytes near OLE object activation and splits the byte stream with whitespace or an ignorable RTF group. This is an Equation Editor OLE activation surface commonly used by CVE-2017-11882 / CVE-2018-0802 exploit documents.
\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 ~1792KB of hex-encoded data inside \objdata sections — may hide a payload
OLE object data medium RTF_OBJDATA

RTF contains 2 \objdata section(s) — embedded OLE objects

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`objdata_00_off00001e1f.bin` `f4bc21b1df098dd3d94911bf89158c6fe032a067cf84e79ce3927d72fbfcc4a0`	rtf-objdata-decoded	RTF \objdata at offset 0x1E1F	896340 bytes

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