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

Trojan:MSIL/FormBook.ABF!MTB - Windows Defender Threat Analysis

$ cat analysis.txt
=== THREAT ANALYSIS REPORT ===
Threat Name: Trojan:MSIL/FormBook.ABF!MTB
Classification:
Type:Trojan
Platform:MSIL
Family:FormBook
Detection Type:Concrete
Known malware family with identified signatures
Variant:ABF
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 - Appears legitimate but performs malicious actions for .NET (Microsoft Intermediate Language) platform, family FormBook

Summary:

Trojan:MSIL/FormBook.ABF!MTB is a concrete detection of the FormBook information-stealing malware, specifically targeting .NET applications. This variant, identified through machine learning behavioral analysis, aims to compromise systems and exfiltrate sensitive data, potentially using lures or disguises related to Vietnamese educational or student management applications.

Severity:
Critical
VDM Static Detection:
Relevant strings associated with this threat:
 - GUI_Services.CanBoGiaoVienGUI (PEHSTR_EXT)
 - GUI_Services.DanhSachGV1Lop (PEHSTR_EXT)
 - GUI_Services.DanhSachHocSinh (PEHSTR_EXT)
 - GUI_Services.PhanCongGiangDayGUI (PEHSTR_EXT)
 - GUI_Services.QuanLyHoSoHocSinh (PEHSTR_EXT)
 - GUI_Services.QuanLyLopGUI (PEHSTR_EXT)
 - GUI_Services.QuanLyMonHocGUI (PEHSTR_EXT)
 - GUI_Services.ThongTinGUI (PEHSTR_EXT)
YARA Rule:
rule Trojan_MSIL_FormBook_ABF_2147900366_0
{
    meta:
        author = "threatcheck.sh"
        detection_name = "Trojan:MSIL/FormBook.ABF!MTB"
        threat_id = "2147900366"
        type = "Trojan"
        platform = "MSIL: .NET intermediate language scripts"
        family = "FormBook"
        severity = "Critical"
        info = "MTB: Microsoft Threat Behavior"
        signature_type = "SIGNATURE_TYPE_PEHSTR_EXT"
        threshold = "2"
        strings_accuracy = "High"
    strings:
        $x_2_1 = {16 13 07 2b 15 11 06 11 07 91 13 08 00 11 08 04 61 13 09 00 11 07 17 58 13 07 11 07 11 06 8e 69 32 e3}  //weight: 2, accuracy: High
    condition:
        (filesize < 20MB) and
        (all of ($x*))
}
Known malware which is associated with this threat:
Filename: IMG_0001.exe
6a6af729bcfe6c368c81300a7b3f078b6077b365d7dad49b9c0bc4d1ee3f71b2
26/01/2026
→VirusTotal↓Download Sample
Remediation Steps:
Immediately isolate the infected system from the network. Perform a full, deep scan with updated antivirus software and remove all detected malicious files. Reset all user credentials, especially for online services and critical accounts, as FormBook is an infostealer. Investigate the initial compromise vector to prevent future infections.
=== END REPORT ===
$ reanalyze-threat
This analysis was last updated on 26/01/2026. Do you want to analyze it again?
$ ls available-commands/
→ cd /home
user@threatcheck.sh:~$ ▊