RTF / .DOC malware analysis — malicious · 93b7b31f375aa3bd

MALICIOUS

RTF / .DOC

1.65 MB First seen: 2022-03-17

MD5: 8dd60a0afc01bc7c1a1e3c6d5f844ce1 SHA-1: d0e75d5b44cee0a6d7e40454ea328494649f4766 SHA-256: 93b7b31f375aa3bd37e131c4aacd4a4301ad8596d4c4d264258569fe0680c997

220 Risk Score

Malware Insights

MITRE ATT&CK

T1566.001 Spearphishing Attachment T1204.002 Malicious File

The sample is an RTF file containing OLE object data, specifically triggering critical heuristics for RTF_EQUATION_EDITOR and CVE_2017_11882_RELATED. The presence of ".bin [rtf-objdata-decoded] 860747 bytes" indicates a significant embedded payload. The ".objupdate forces OLE activation" heuristic suggests that the embedded object is designed to be automatically executed upon opening the document. This points to an exploitation attempt using CVE-2017-11882 to deliver a secondary payload.

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 ~1721KB 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_off000013d3.bin` `8e9db612674a57cce24db02bff7690c68e61582fb77378a840c7198d75597345`	rtf-objdata-decoded	RTF \objdata at offset 0x13D3	860747 bytes

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