user@threatcheck.sh ~ threat-analysis
bash
$ analyze-threat Backdoor:MSIL/Crysen!rfn
Backdoor:MSIL/Crysen!rfn - Windows Defender threat signature analysis

Backdoor:MSIL/Crysen!rfn - Windows Defender Threat Analysis

$ cat analysis.txt
=== THREAT ANALYSIS REPORT ===
Threat Name: Backdoor:MSIL/Crysen!rfn
Classification:
Type:Backdoor
Platform:MSIL
Family:Crysen
Detection Type:Concrete
Known malware family with identified signatures
Suffix:!rfn
Specific ransomware family name
Confidence:Very High
False-Positive Risk:Low

Concrete signature match: Backdoor - Provides unauthorized remote access for .NET (Microsoft Intermediate Language) platform, family Crysen

Summary:

Backdoor:MSIL/Crysen!rfn is a sophisticated .NET backdoor that establishes persistent remote access and executes commands by abusing legitimate system tools like scheduled tasks, PowerShell, rundll32, and BITS jobs. It features capabilities for API hooking, privilege escalation, and robust C2 communication to maintain control over the compromised system.

Severity:
Critical
VDM Static Detection:
Relevant strings associated with this threat:
 - /c schtasks /create /f /sc onlogon /ru system /rl highest /tn (PEHSTR_EXT)
 - \nuR\noisreVtnerruC\swodniW\tfosorciM\erawtfoS (PEHSTR_EXT)
 - masterKey can not be null or empty. (PEHSTR_EXT)
 - set_UseShellExecute (PEHSTR_EXT)
 - Client.Install (PEHSTR_EXT)
 - Client.Helper (PEHSTR_EXT)
 - Client.Handle_Packet (PEHSTR_EXT)
 - System.Threading (PEHSTR_EXT)
 - System.Reflection.Emit (PEHSTR_EXT)
 - !#HSTR:StringCodeForMshta.A!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForHooking.C!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForHooking.D!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForHooking.L!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForHooking.O!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForRegsvr32.A!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForRundll32.A!pli (PEHSTR_EXT)
 - rundll32 (PEHSTR_EXT)
 - !#HSTR:StringCodeForBITSJobs.A!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForPowerShell.G!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForScheduledTask.A!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForDataEncoding.D!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForHooking.J!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForHooking.K!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForRemoteFileCopy.B!pli (PEHSTR_EXT)
 - !#HSTR:ExecutionGuardrails (PEHSTR_EXT)
 - !#HSTR:StringCodeForFileDeletion.A!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForHooking.M!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForNetshHelperDLL.A!pli (PEHSTR_EXT)
 - !#HSTR:StringCodeForRemoteServices.A!pli (PEHSTR_EXT)
Known malware which is associated with this threat:
Filename: 024b910085ff5f6fcb777f5470a61e05ca176159186ec.exe
024b910085ff5f6fcb777f5470a61e05ca176159186ec892aeeb3f47f9a23247
26/12/2025
→VirusTotal↓Download Sample
Remediation Steps:
Immediately isolate the infected system, perform a full system scan with updated antivirus/EDR, remove all detected malicious files, and meticulously review and remove all persistence mechanisms (e.g., scheduled tasks, startup entries). Due to the confirmed backdoor nature and high privileges, a full system re-image is strongly recommended after backing up critical data.
=== END REPORT ===
$ reanalyze-threat
This analysis was last updated on 26/12/2025. Do you want to analyze it again?
$ ls available-commands/
→ cd /home
user@threatcheck.sh:~$ ▊