Fallout from the Dutch Server Seizures: Auditing for 'Stark' Residuals
Just caught the latest update from KrebsOnSecurity regarding the Dutch authorities seizing 800 servers and arresting two co-owners linked to hosting infrastructure used by Russian intelligence. It turns out these outfits had absorbed the infrastructure previously run by 'Stark Industries Solutions,' which the EU sanctioned last year.
This takedown is significant because it disrupts a major staging ground for influence ops and cyberattacks within the EU. However, the key concern for us now is identifying if any of our infrastructure communicated with these malicious nodes before they went dark. Since specific CVEs aren't the primary vector here, we need to focus on network-level IOC hunting.
If you are reviewing your logs, I recommend checking for historical connections to the specific Autonomous System Numbers (ASNs) associated with these providers. You can use a KQL query similar to this to hunt for residual traffic in Sentinel or Microsoft 365 Defender:
DeviceNetworkEvents
| where RemoteIP in ("ip_range_1", "ip_range_2") // Replace with seized IP ranges
| project Timestamp, DeviceName, InitiatingProcessFileName, RemoteIP, RemotePort
| summarize count() by bin(Timestamp, 1h), DeviceName, RemoteIP
Additionally, be wary of any dormant VPS instances or scheduled tasks that might be attempting heartbeats to these now-seized servers, as this could indicate a persistent backdoor installed by related threat actors.
How are you guys handling third-party hosting risk assessments? Do you maintain an internal blocklist of 'high-risk' ASNs, or is that too noisy for your environment?
Solid advice on the KQL hunting. We actually block known 'bulletproof' hosting ASNs at the perimeter firewall as a matter of policy. It generates some noise with false positives—usually devs spinning up cheap test boxes—but the reduction in C2 callbacks is worth the trouble. For those interested, I recommend cross-referencing the seized IPs against your firewall logs using grep:
grep -E "192.0.2\.|198.51\.100\." /var/log/firewall.log | awk '{print $1, $2, $3}'
Just replace the dummy IPs with the actual ranges from the Krebs report.
This highlights the danger of 'BGP poisoning' or simply buying infrastructure from shady resellers. We had a client last year who bought a 'dedicated server' from a no-name provider that turned out to be part of a botnet. The IP was blacklisted by Microsoft within a week.
We've started incorporating RiskIQ (or PassiveTotal) lookups into our onboarding checklist for any new external IP usage. If the IP has a 'high risk' score or history of malware hosting, we reject it immediately.
From a pentester perspective, it's always fascinating to see how these actors pivot. Stark Industries was notorious for being a 'proxy' service. Taking down the servers stops the bleeding, but the operators likely have backups. I'd suggest looking for anomalous PowerShell processes that might be trying to reach out to new fallback domains.
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4688} | Where-Object {$_.Message -match 'powershell.exe'} | Select-Object TimeCreated, Message
Don't assume the threat is gone just because the servers are seized; the rats will look for a new ship.
While blocking ASNs is smart, don't forget to check for application-level persistence. Actors using this infrastructure often leave behind webshells for lateral movement, which won't be stopped by perimeter rules.
You should run a YARA scan over your webroots for common obfuscation patterns found in their PHP droppers:
yara rule Stark_Dropper_Hunt { strings: $obfuscation = /eval\s*(.*base64_decode/ nocase $marker = "stark" nocase condition: uint16(0) == 0x3C3F and 1 of them }
Solid points on persistence. Since we're looking at residuals, don't overlook memory-resident artifacts that standard disk scans miss. These groups often use process hollowing to hide payloads. If you have memory captures, running Volatility to find suspicious injected threads is a must:
vol.py -f image.mem windows.malfind
This helps catch payloads that might survive disk wipes or file deletion, ensuring the host is actually clean.
Excellent thread. While we hunt for technical artifacts, don't overlook the identity angle. If these servers were used as a jump box, valid credentials might be compromised. Audit your IdP for any successful sign-ins or MFA challenges originating from the seized IP ranges immediately.
Here is a quick KQL query for Entra ID:
SigninLogs
| where IPAddress in ("", "")
| summarize Count = count() by UserPrincipalName, AppDisplayName
This helps confirm if attackers established persistence via authorized users before the takedown.
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