user@threatcheck.sh ~ threat-analysis
bash
$ analyze-threat TrojanDownloader:MSIL/FormBook.D!MTB
TrojanDownloader:MSIL/FormBook.D!MTB - Windows Defender threat signature analysis

TrojanDownloader:MSIL/FormBook.D!MTB - Windows Defender Threat Analysis

$ cat analysis.txt
=== THREAT ANALYSIS REPORT ===
Threat Name: TrojanDownloader:MSIL/FormBook.D!MTB
Classification:
Type:TrojanDownloader
Platform:MSIL
Family:FormBook
Detection Type:Concrete
Known malware family with identified signatures
Variant:D
Specific signature variant within the malware family
Suffix:!MTB
Detected via machine learning and behavioral analysis
Detection Method:Behavioral
Confidence:Very High
False-Positive Risk:Low

Concrete signature match: Trojan Downloader - Downloads additional malware for .NET (Microsoft Intermediate Language) platform, family FormBook

Summary:

This is a concrete detection of FormBook, a notorious MSIL-based information stealer. Functioning as a trojan downloader, it is designed to retrieve and execute secondary malicious payloads, likely after decrypting and decoding them. Its primary objective is typically data exfiltration, including credentials and financial information.

Severity:
Critical
VDM Static Detection:
Relevant strings associated with this threat:
 - WDCWCFDRR (PEHSTR_EXT)
 - GetMethods (PEHSTR_EXT)
 - DefineByValTStrRemotingServices (PEHSTR_EXT)
 - DownloadData (PEHSTR_EXT)
 - CreateDecryptor (PEHSTR_EXT)
 - |#d1e49aac-8f56-4280-b9ba-993a6d77406c (NID)
 - }#d1e49aac-8f56-4280-b9ba-993a6d77406c (NID)
 - &|#b2b3f03d-6a65-4f7b-a9c7-1c7ef74a9ba4 (NID)
 - &}#b2b3f03d-6a65-4f7b-a9c7-1c7ef74a9ba4 (NID)
 - C|#be9ba2d9-53ea-4cdc-84e5-9b1eeee46550 (NID)
 - C}#be9ba2d9-53ea-4cdc-84e5-9b1eeee46550 (NID)
 - |#5beb7efe-fd9a-4556-801d-275e5ffc04cc (NID)
 - }#5beb7efe-fd9a-4556-801d-275e5ffc04cc (NID)
 - |#01443614-cd74-433a-b99e-2ecdc07bfc25 (NID)
 - }#01443614-cd74-433a-b99e-2ecdc07bfc25 (NID)
 - |#d3e037e1-3eb8-44c8-a917-57927947596d (NID)
 - }#d3e037e1-3eb8-44c8-a917-57927947596d (NID)
 - |#92e97fa1-2edf-4476-bdd6-9dd0b4dddc7b (NID)
 - }#92e97fa1-2edf-4476-bdd6-9dd0b4dddc7b (NID)
 - |#c1db55ab-c21a-4637-bb3f-a12568109d35 (NID)
 - }#c1db55ab-c21a-4637-bb3f-a12568109d35 (NID)
 - |#26190899-1602-49e8-8b27-eb1d0a1ce869 (NID)
 - }#26190899-1602-49e8-8b27-eb1d0a1ce869 (NID)
 - |#e6db77e5-3df2-4cf1-b95a-636979351e5b (NID)
 - }#e6db77e5-3df2-4cf1-b95a-636979351e5b (NID)
YARA Rule:
rule TrojanDownloader_MSIL_FormBook_D_2147900930_0
{
    meta:
        author = "threatcheck.sh"
        detection_name = "TrojanDownloader:MSIL/FormBook.D!MTB"
        threat_id = "2147900930"
        type = "TrojanDownloader"
        platform = "MSIL: .NET intermediate language scripts"
        family = "FormBook"
        severity = "Critical"
        info = "MTB: Microsoft Threat Behavior"
        signature_type = "SIGNATURE_TYPE_PEHSTR_EXT"
        threshold = "4"
        strings_accuracy = "Low"
    strings:
        $x_2_1 = {70 20 00 01 00 00 14 14 14 6f ?? 00 00 0a 26 20}  //weight: 2, accuracy: Low
        $x_1_2 = "CreateDecryptor" ascii //weight: 1
        $x_1_3 = "FromBase64String" ascii //weight: 1
    condition:
        (filesize < 20MB) and
        (all of ($x*))
}
Known malware which is associated with this threat:
dbb7037739e18719252cfa1a63a76c12eb9a5ad6f3ae2d1e4d369ca0544a199d
21/12/2025
→VirusTotal↓Download Sample
Remediation Steps:
Immediately isolate the affected system to prevent further network compromise. Perform a full scan with up-to-date antivirus and remove all detected threats. Investigate for signs of data exfiltration and additional malware installations, and consider a clean system rebuild from a trusted backup.
=== END REPORT ===
$ reanalyze-threat
This analysis was last updated on 21/12/2025. Do you want to analyze it again?
$ ls available-commands/
→ cd /home
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