RTF malware analysis — malicious · f91c3b957fcbbcfa

MALICIOUS

RTF

3.54 MB First seen: 2022-07-19

MD5: 4648929a51dff64996ceadf443afdde7 SHA-1: 7d8df64142fa797bba2df7e9ae634aaf1dd32afb SHA-256: f91c3b957fcbbcfa550282692e15b1c279f31a1dfdd3a21d0473579f89d36f44

442 Risk Score

Malware Insights

MITRE ATT&CK

T1204 Malicious Link T1204.002 Malicious File T1059 Command and Scripting Interpreter T1059.003 Windows Command Shell T1566 Phishing T1566.001 Spearphishing Attachment

The RTF file contains embedded OLE objects and exploits the CVE-2017-11882 vulnerability in Microsoft Equation Editor to activate and execute a payload. ClamAV detections indicate the embedded artifact is a Remote Access Trojan (RAT), specifically identified as AsyncRAT. The presence of the Equation Editor exploit and the embedded PE file strongly suggests a malicious dropper.

Heuristics 11

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.
Composite Moniker in RTF OLE object high CVE related RTF_COMPOSITE_MONIKER_RELATED

RTF contains Composite Moniker CLSID in OLE object context, but no nearby scriptlet/SCT payload was confirmed. Treat as related moniker attack-surface evidence rather than proof of CVE-2017-8570 exploitation.
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 ~1677KB 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` `73a04e333a71c2c4dd42a86597d3a59afd8792c58355d225a233806f96952f2a`	rtf-objdata-decoded	RTF \objdata at offset 0x129E	856363 bytes
Detection ClamAV: Win.Trojan.AsyncRAT-9914220-0 Obfuscation or payload: likely Carved artifact entropy is 7.89, consistent with packed or encrypted content.
`objdata_01_off001aee56.bin` `ee689f3f3e104d316fdfdcc5da12c6430bbbcc7bd0a9e503676477f2b53390b6`	rtf-objdata-decoded	RTF \objdata at offset 0x1AEE56	462748 bytes

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