RTF malware analysis — malicious · f8804b3f14902046

MALICIOUS

RTF

2.41 MB First seen: 2022-07-28

MD5: 7636b1bf58ad69e870b546b11fc5678a SHA-1: f5debcc7e3d0644dc111f6ca04948947b030cda2 SHA-256: f8804b3f149020463636686c55f23a4c12ceea1a9cba913cede1099f24033f2e

402 Risk Score

Malware Insights

MITRE ATT&CK

T1204 Malicious Link T1204.001 Malicious Link: Malicious Link T1559 Component Object Model Hijacking T1559.001 Component Object Model Hijacking: Component Object Model Hijacking T1059 Command and Scripting Interpreter T1059.001 Command and Scripting Interpreter: PowerShell T1059.003 Command and Scripting Interpreter: Windows Command Shell

The RTF document contains embedded OLE objects and exploits the Equation Editor vulnerability (CVE-2017-11882) to execute arbitrary code. ClamAV detections indicate it functions as a dropper for a payload, identified as AsyncRAT. The embedded hex data likely contains the second-stage malware.

Heuristics 10

Equation Editor activation — CVE-2017-11882 related high CVE related CVE_2017_11882_ACTIVATION_RELATED

RTF decodes to an Equation.3 ProgID and requests OLE activation with \objemb plus \objupdate. This reaches the legacy Equation Editor attack surface used by CVE-2017-11882/CVE-2018-0802 documents, but the malformed MTEF/native payload needed for stronger 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.
PE header (with DOS stub) in hex data critical RTF_MZ_HEX

Hex-encoded PE (MZ + DOS stub) found inside RTF — likely an embedded executable payload
ClamAV: Rtf.Dropper.Agent-9965975-1 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Rtf.Dropper.Agent-9965975-1
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.
\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 ~1795KB 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
Embedded OLE object medium RTF_OBJEMB

RTF contains \objemb — embedded OLE object
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
`objdata_00_off0000129e.bin` `b4a8420210c11dd796ebc90bea1e67699430ca468ab49e995506012129e9b94b`	rtf-objdata-decoded	RTF \objdata at offset 0x129E	903493 bytes
Detection ClamAV: Win.Trojan.AsyncRAT-9914220-0 Obfuscation or payload: likely Carved artifact entropy is 7.60, consistent with packed or encrypted content.
`objdata_01_off001c06a6.bin` `be008ac939deab73a9c9495546d8254146b2be045989f91ea9153bd4e8489f59`	rtf-objdata-decoded	RTF \objdata at offset 0x1C06A6	140002 bytes

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