TrickBot DNS Tunneling Variant: C2 Infrastructure & Persistence Analysis

Threat Summary

A distinct variant of the TrickBot banking trojan (S0266) has been identified utilizing DNS tunneling for Command and Control (C2) communications, a shift from the traditional HTTP/HTTPS protocols typically employed by this modular malware family. This adaptation suggests an active effort by threat actors to bypass network inspection controls often configured for web traffic. The campaign leverages NTFS Alternate Data Streams (ADS) for configuration storage and Windows Task Scheduler for high-persistence, establishing a resilient foothold on infected endpoints likely for credential harvesting and lateral movement within banking and enterprise environments.

Threat Actor / Malware Profile

Malware Family: TrickBot (Variant: Totbrick, TSPY_TRICKLOAD)

Distribution Method: While the specific initial vector for this specific wave is not detailed in the pulse, TrickBot is historically distributed via massive malspam campaigns wielding malicious attachments (e.g., Excel macros with embedded PowerShell) or via post-exploitation propagation by loaders like Emotet.

Payload Behavior:

Modular Architecture: TrickBot loads plugins dynamically. This variant includes modules specifically tuned for DNS tunneling.
Configuration Storage: Utilizes NTFS Alternate Data Streams to hide configuration data and modules within legitimate files, evading standard file-system scanning.

C2 Communication:

Protocol: DNS Tunneling. The malware encodes data into subdomain queries or TXT records sent to the authoritative DNS server controlled by the actor (westurn.in). This method blends in with legitimate DNS traffic and is difficult to block without impacting business operations.

Persistence Mechanism:

Windows Task Scheduler: Creates disguised tasks scheduled to execute at system startup and repeated every five minutes to ensure rapid re-establishment of C2 if the process is terminated.

Anti-Analysis Techniques:

Obfuscation: Heavily obfuscated code and use of ADS to hide artifacts.
Process Injection: Common in TrickBot variants to inject malicious code into legitimate Windows processes (e.g., explorer.exe), masking execution flow.

IOC Analysis

The current pulse provides a focused set of indicators centered on a specific domain and sample hashes.

Domains: westurn.in. This is the primary sinkhole/C2 domain for the DNS tunneling. SOC teams should immediately block this domain at the DNS forwarder and firewall level.
File Hashes: A collection of MD5, SHA1, and SHA256 hashes corresponding to the malware loader and modules.
- Operationalization: Feed these hashes into EDR solutions for historical scanning. Investigate any endpoints with a hit history for process execution or file creation events matching these hashes.
Tooling: YARA rules can be generated from the samples to detect memory injection patterns, and Sigma rules (below) are provided for behavioral detection of the DNS tunneling and persistence mechanisms.

Detection Engineering

YAML

---
title: TrickBot Scheduled Task Persistence
id: 0a1b2c3d-4e5f-6789-0123-456789abcdef
description: Detects the creation of scheduled tasks that match TrickBot persistence patterns, specifically recurring every 5 minutes or utilizing common disguise names.
status: experimental
date: 2026/07/23
author: Security Arsenal
references:
    - https://www.fortinet.com/blog/threat-research/inside-a-trickbot-variant-using-dns-tunneling-for-c2
tags:
    - attack.persistence
    - attack.s0111
    - attack.t1053.005
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 4698
        TaskName|contains:
            - 'Update'
            - 'Flash'
            - 'System'
            - 'Chrome'
    condition: selection | count(TaskName) by TaskName > 3
falsepositives:
    - Legitimate software updates
level: high
---
title: Suspicious DNS Tunneling Activity
id: b2c3d4e5-6f78-9012-3456-7890abcdef12
description: Detects potential DNS tunneling by identifying long DNS query lengths and high volume of requests to a single domain, characteristic of TrickBot C2.
status: experimental
date: 2026/07/23
author: Security Arsenal
references:
    - https://www.fortinet.com/blog/threat-research/inside-a-trickbot-variant-using-dns-tunneling-for-c2
tags:
    - attack.command_and_control
    - attack.t1071.004
logsource:
    product: windows
    service: dns
detection:
    selection:
        QueryLength|gte: 40
    condition: selection | count() by QueryName > 10
 timeframe: 1m
falsepositives:
    - Heavy CDN usage
    - Specific security software updates
level: medium
---
title: NTFS Alternate Data Stream Access via PowerShell
id: c3d4e5f6-7890-1234-5678-90abcdef1234
description: Detects access to NTFS Alternate Data Streams, a method used by TrickBot to store configuration data hidden from standard views.
status: experimental
date: 2026/07/23
author: Security Arsenal
references:
    - https://www.fortinet.com/blog/threat-research/inside-a-trickbot-variant-using-dns-tunneling-for-c2
tags:
    - attack.defense_evasion
    - attack.t1564.004
logsource:
    product: windows
    service: security
detection:
    selection_cmd:
        EventID: 4688
        NewProcessName|endswith: '\powershell.exe'
        CommandLine|contains: ':$DATA'
    selection_ps:
        EventID: 4103
        Payload|contains: 'Get-Content'
        Payload|contains: 'Stream'
    condition: 1 of selection*
falsepositives:
    - Administrative scripts managing file metadata
level: medium


kql
// KQL Hunt for TrickBot DNS Tunneling and Persistence
// Hunt for the specific C2 domain
DeviceNetworkEvents
| where Timestamp > ago(7d)
| where RemoteUrl has "westurn.in" 
| project Timestamp, DeviceName, InitiatingProcessFileName, RemoteUrl, RemotePort

// Hunt for high frequency DNS requests (potential tunneling)
DeviceNetworkEvents 
| where Timestamp > ago(24h)
| where ActionType == "DnsQuery"
| extend QueryLength = strlen(RemoteUrl)
| where QueryLength > 30
| summarize count() by RemoteUrl, DeviceName, bin(Timestamp, 5m)
| where count_ > 10

// Hunt for Scheduled Task creation events
DeviceProcessEvents
| where Timestamp > ago(7d)
| where FileName =~ "schtasks.exe"
| where ProcessCommandLine has "create" or ProcessCommandLine has "change"
| project Timestamp, DeviceName, AccountName, ProcessCommandLine


powershell
# PowerShell Hunt Script for TrickBot IOCs and Persistence
# Requires Administrator privileges for comprehensive scanning

$TargetHashes = @(
    "8d5b3a0512744efc132afa6fc75c64d8",
    "f7f2f482f3bc6345a44e4a6d647731ae",
    "48fd2036b6556c6747197e07f1706bcf58a27518",
    "105f652e6b8f31c371f2385877e43b6772aff5d3168d5d4635f8a1fcbb321421",
    "33c331ededbf8ee9829895424423ce3fd17e359d2e784fcbce396aacff458cf5",
    "3b19a82e1354ac14a3da7c840cbdd0ce50db38432d784767b36f08e45024c23d",
    "6c677eb2b3ffd288083c59a13d7bb712d4754af61a5563873f76c440962346f4"
)

Write-Host "[+] Scanning for TrickBot Scheduled Tasks..." -ForegroundColor Yellow
Get-ScheduledTask | Where-Object { 
    $_.State -eq 'Ready' -and 
    ($_.Actions.Execute -like '*powershell*' -or $_.Actions.Execute -like '*cmd*') -and
    ($_.Triggers.Repetition.Interval -eq 'PT5M')
} | Select-Object TaskName, TaskPath, Actions, Triggers

Write-Host "[+] Scanning specific directories for file hashes..." -ForegroundColor Yellow
$PathsToScan = @("C:\Users\", "C:\Windows\Temp", "C:\ProgramData")

foreach ($Path in $PathsToScan) {
    if (Test-Path $Path) {
        Get-ChildItem -Path $Path -Recurse -ErrorAction SilentlyContinue | Get-FileHash -Algorithm MD5 -ErrorAction SilentlyContinue | 
        Where-Object { $TargetHashes -contains $_.Hash } | 
        Select-Object Path, Hash, Algorithm
    }
}

Write-Host "[+] Checking for DNS Cache entry for westurn.in..." -ForegroundColor Yellow
Get-DnsClientCache | Where-Object { $_.Entry -like "*westurn*" }

Response Priorities

Immediate (0-4 hours):
- Block the domain westurn.in at all DNS resolvers and perimeter firewalls.
- Execute the PowerShell hunt script across the enterprise to identify infected hosts.
- Isolate any endpoints returning positive matches for the provided file hashes.
24 Hours:
- Conduct credential resets for accounts logged into infected endpoints (focus on banking/finance and admin credentials).
- Review Windows Event Logs (Security ID 4688 and 4698) on compromised hosts to determine the scope of scheduled task manipulation.
1 Week:
- Implement DNS monitoring rules to alert on high-entropy or long-length DNS queries (>50 chars) to detect future tunneling attempts.
- Update EDR policies to flag access to NTFS Alternate Data Streams by non-administrative tools.

Related Resources

Security Arsenal Incident Response Managed SOC & MDR Services AlertMonitor Threat Detection From The Dark Side Intel Hub