RTF / .DOC malware analysis — malicious · 16c90d0803ddb8be

MALICIOUS

RTF / .DOC

1.62 MB First seen: 2023-02-13

MD5: ecbfb5fb0eda1d1f9bbfcf88823257cb SHA-1: 3d43da3458ad1f770ac555968a4dd1832cff3756 SHA-256: 16c90d0803ddb8beafa954da60ae5463fcf943e7bc8ca9d3cc235e716ec37c9a

222 Risk Score

Malware Insights

MITRE ATT&CK

T1566.001 Spearphishing Attachment T1204.002 Malicious File T1059.003 Windows Command Shell

The sample is an RTF document containing an OLE object that exploits the Equation Editor vulnerability (CVE-2017-11882). The heuristic firings indicate the presence of a decoded Equation Editor payload and a PE file within the OLE object, strongly suggesting it's designed to deliver a second-stage malicious payload. No document body text or scripts were extracted, but the exploit itself is the primary indicator of malicious intent.

Heuristics 6

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.
Decoded Equation Editor payload + PE critical 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.
\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 ~1702KB 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_off00000079.bin` `4059bf7fdffd487c7ebea4dea214918b82da2e29dab180e616482a94365c3781`	rtf-objdata-decoded	RTF \objdata at offset 0x79	851284 bytes
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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