Malicious RTF — malware analysis report

Static analysis result for SHA-256 c6a01f392e4c317e…

MALICIOUS

RTF

729.0 KB Created: 2018-12-12 16:35:00 Authoring application: Microsoft Word 11.0.5604 First seen: 2019-11-20
MD5: 10348b56b0e3466f9f9fa62bda081c98 SHA-1: 2220cf23206846d685195cb91be8529641f18be9 SHA-256: c6a01f392e4c317e6c9b6b3ce860f6368fad7687336ce995246d01fb52b83ca4
342 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF file contains multiple indicators of exploitation targeting the Equation Editor, specifically referencing CVE-2017-11882 and CVE-2018-0798. The presence of OLE object data and the ".objupdate" directive strongly suggest that the embedded Equation Editor object is designed to be activated, leading to arbitrary code execution. The ClamAV detection as Rtf.Dropper.Agent-6848954-0 further confirms its malicious nature as a dropper.

Heuristics 9

  • Equation Editor CLSID critical CVE likely RTF_EQUATION_EDITOR
    Equation Editor OLE CLSID found inside an OLE object — exploited by CVE-2017-11882 / CVE-2018-0802 / CVE-2018-0798
  • CVE-2018-0798 — Equation Editor Matrix record overflow critical CVE exact CVE_2018_0798
    RTF contains hex-encoded MTEF Matrix record exploit signature (NOP-sled 0x60 + padding 0x61 + return address 0x0BFB). CVE-2018-0798 exploits a stack buffer overflow in EQNEDT32.EXE's Matrix record parser and affected Equation Editor broadly, including builds patched for CVE-2017-11882. Widely used by APT groups (Conimes, KeyBoy, Emissary Panda, Rancor).
  • 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.
  • ClamAV: Rtf.Dropper.Agent-6848954-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Rtf.Dropper.Agent-6848954-0
  • \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.
  • Package object class high RTF_OBJCLASS_PACKAGE
    OLE Package object — can wrap arbitrary files
  • OLE object data medium RTF_OBJDATA
    RTF contains 3 \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 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off0000a46a.bin rtf-objdata-decoded RTF \objdata at offset 0xA46A 340208 bytes
SHA-256: b75c5bf210e9126b6f4d138846f3ebe38ee5ba468c54b7f0d99fe9ce6b3d698f
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact entropy is 7.77, consistent with packed or encrypted content.
objdata_01_off000b0680.bin rtf-objdata-decoded RTF \objdata at offset 0xB0680 11842 bytes
SHA-256: 82a0e9d2b46fe974ae1d3298ffd405eb8e6ea8fda7665fef57d4e0d76c604d9d
objdata_02_off000b0692.bin rtf-objdata-decoded RTF \objdata at offset 0xB0692 35 bytes
SHA-256: d0771b17e6418e479f528fc4aa124822669975a78f8dc3e35cdc4b0f7c212c4e

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