Malicious RTF — malware analysis report

Static analysis result for SHA-256 b45087ad4f7d8475…

MALICIOUS

RTF

795.9 KB Created: 2018-03-16 14:52:00 Authoring application: Microsoft Word 11. 0.5604 First seen: 2019-08-04
MD5: e228045ef57fb8cc1226b62ada7eee9b SHA-1: 4532b6f08b0d71893394e74e591a943bbc625f1c SHA-256: b45087ad4f7d84758046e9d6eb174530fee98b069105a78f124cbde1ecfb0415
342 Risk Score

Malware Insights

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

The file is an RTF document that exploits known vulnerabilities in the Microsoft Equation Editor (CVE-2017-11882 and CVE-2018-0798). These exploits are designed to download and execute a secondary payload, indicated by the 'Dropper' detection from ClamAV. The document body content appears to be legitimate Vietnamese government regulations, suggesting a lure to entice users to open the document.

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-7117863-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Rtf.Dropper.Agent-7117863-0
  • \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_off0001afd3.bin rtf-objdata-decoded RTF \objdata at offset 0x1AFD3 340208 bytes
SHA-256: 721fb04a7c86e308f8122dd672bc943dc49b2133f1b8d6af88ff0d6e8ced10cf
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact entropy is 7.77, consistent with packed or encrypted content.
objdata_01_off000c11e9.bin rtf-objdata-decoded RTF \objdata at offset 0xC11E9 11842 bytes
SHA-256: 82a0e9d2b46fe974ae1d3298ffd405eb8e6ea8fda7665fef57d4e0d76c604d9d
objdata_02_off000c11fb.bin rtf-objdata-decoded RTF \objdata at offset 0xC11FB 35 bytes
SHA-256: d0771b17e6418e479f528fc4aa124822669975a78f8dc3e35cdc4b0f7c212c4e

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