Malicious RTF — malware analysis report

Static analysis result for SHA-256 81f75839e6193212…

MALICIOUS

RTF

699.6 KB Created: 2016-12-14 10:27:00 Authoring application: Microsoft Word 11.0.5604 First seen: 2019-11-20
MD5: 84fca27bc75f40194c95534b07838d6c SHA-1: 9520a18e9f6d4f6f014aa576b8843cdff176f701 SHA-256: 81f75839e6193212d71d771edea62430111482177cdc481f4688d82cd8a5fed6
342 Risk Score

Malware Insights

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

The RTF document contains multiple indicators of exploitation targeting Microsoft Equation Editor, specifically referencing CVE-2017-11882 and CVE-2018-0798. The presence of OLE objects and the ".objupdate" directive strongly suggest that the document is designed to trigger these vulnerabilities upon opening. This is consistent with a malicious dropper designed to execute a secondary payload, as indicated by the ClamAV detection name 'Rtf.Dropper.Agent-6837941-0'.

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-6837941-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Rtf.Dropper.Agent-6837941-0
  • \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_off00003eb1.bin rtf-objdata-decoded RTF \objdata at offset 0x3EB1 338160 bytes
SHA-256: b9499bf596880d5406fa352166abc76e41851774fd97926b6b55512b85f30050
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact entropy is 7.81, consistent with packed or encrypted content.
objdata_01_off000a90c7.bin rtf-objdata-decoded RTF \objdata at offset 0xA90C7 11842 bytes
SHA-256: 82a0e9d2b46fe974ae1d3298ffd405eb8e6ea8fda7665fef57d4e0d76c604d9d
objdata_02_off000a90d9.bin rtf-objdata-decoded RTF \objdata at offset 0xA90D9 35 bytes
SHA-256: d0771b17e6418e479f528fc4aa124822669975a78f8dc3e35cdc4b0f7c212c4e

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