Eradicating Malware From Infected Systems

---
name: eradicating-malware-from-infected-systems
description: Systematically remove malware, backdoors, and attacker persistence mechanisms from infected systems while ensuring complete eradication and preventing re-infection.
tags:
- malware-removal
- incident-response
- persistence
- fetih
- dfir
- cybersecurity
- siber-güvenlik
- eradication
triggers:
- IR
- api
- breach
- eradicating
- forensic
- güvenlik olayı
- hash
- http
- incident response
- infected
- log
- malware
category: incident-response
source_subdomain: incident-response
mitre_attack:
- T1547
- T1053
- T1543
- T1574
nist_csf:
- RS.MA-01
- RS.MA-02
- RS.AN-03
- RC.RP-01
adapted_for: fetih
---

# Eradicating Malware from Infected Systems


## Ne Zaman Kullanılır
- Malware infection confirmed and containment is in place
- Forensic investigation has identified all persistence mechanisms
- All compromised systems have been identified and scoped
- Ready to remove attacker artifacts and restore clean state
- Post-containment phase requires systematic cleanup

## Ön Gereksinimler
- Completed forensic analysis identifying all malware artifacts
- List of all compromised systems and accounts
- EDR/AV with updated signatures Dağıtılmış
- YARA rules for the specific malware family
- Clean system images or verified backups for restoration
- Network isolation still in effect during eradication

## İş Akışı

### Adım 1: Map All Persistence Mechanisms
```bash
autorunsc.exe -accepteula -a * -c -h -s -v > autoruns_report.csv

reg query "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /s
reg query "HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /s
reg query "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce" /s
reg query "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run" /s

schtasks /query /fo CSV /v > schtasks_all.csv

Get-WMIObject -Namespace root\Subscription -Class __EventFilter
Get-WMIObject -Namespace root\Subscription -Class CommandLineEventConsumer
Get-WMIObject -Namespace root\Subscription -Class __FilterToConsumerBinding

Get-Service | Where-Object {$_.Status -eq 'Running'} | Select-Object Name, DisplayName, BinaryPathName

cat /etc/crontab
ls -la /etc/cron.*/
ls -la /etc/init.d/
systemctl list-unit-files --type=service | grep enabled
cat /etc/rc.local
ls -la ~/.bashrc ~/.profile ~/.bash_profile
```

### Adım 2: Identify All Malware Artifacts
```bash
yara -r -s malware_rules/specific_family.yar C:\ 2>/dev/null

clamscan -r --infected --remove=no /mnt/infected_disk/

Bul: / -type f -newer /tmp/baseline_timestamp -exec sha256sum {} \; 2>/dev/null | \
  while read hash file; do
    grep -q "$hash" known_malicious_hashes.txt && echo "MALICIOUS: $file ($hash)"
  done

Bul: /var/www/ -name "*.php" -newer /tmp/baseline -exec grep -l "eval\|base64_decode\|system\|passthru\|shell_exec" {} \;

Bul: / -name "authorized_keys" -exec cat {} \; 2>/dev/null
```

### Adım 3: Remove Malware Files and Artifacts
```bash
Remove-Item -Path "C:\Windows\Temp\malware.exe" -Force
Remove-Item -Path "C:\Users\Public\backdoor.dll" -Force

schtasks /delete /tn "MaliciousTaskName" /f

Get-WMIObject -Namespace root\Subscription -Class __EventFilter -Filter "Name='MalFilter'" | Remove-WMIObject
Get-WMIObject -Namespace root\Subscription -Class CommandLineEventConsumer -Filter "Name='MalConsumer'" | Remove-WMIObject

reg delete "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v "MalEntry" /f

sc stop "MalService" && sc delete "MalService"

crontab -r  # Remove entire crontab (or edit specific entries)
rm -f /tmp/.hidden_backdoor
sed -i '/malicious_key/d' ~/.ssh/authorized_keys
systemctl disable malicious-service && rm /etc/systemd/system/malicious-service.service
```

### Adım 4: Reset Compromised Credentials
```bash
Import-Module ActiveDirectory
Get-ADUser -Filter * -SearchBase "OU=CompromisedUsers,DC=domain,DC=com" |
  Set-ADAccountPassword -Reset -NewPassword (ConvertTo-SecureString "TempP@ss!$(Get-Random)" -AsPlainText -Force)

Reset-KrbtgtPassword -DomainController DC01
Reset-KrbtgtPassword -DomainController DC01

Get-ADServiceAccount -Filter * | ForEach-Object {
  Reset-ADServiceAccountPassword -Identity $_.Name
}

Get-AzureADUser -All $true | ForEach-Object {
  Revoke-AzureADUserAllRefreshToken -ObjectId $_.ObjectId
}

```

### Adım 5: Patch Vulnerability Used for Initial Access
```bash
Install-WindowsUpdate -KBArticleID "KB5001234" -AcceptAll -AutoReboot

apt update && apt upgrade -y  # Debian/Ubuntu
yum update -y                 # RHEL/CentOS


Get-HotFix -Id "KB5001234"
```

### Adım 6: Validate Eradication
```bash
curl -X POST "https://api.crowdstrike.com/scanner/entities/scans/v1" \
  -H "Authorization: Bearer $FALCON_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"ids": ["device_id"]}'

autorunsc.exe -accepteula -a * -c -h -s -v | Bul:str /i "unknown verified"

Get-Process | Where-Object {$_.Path -notlike "C:\Windows\*" -and $_.Path -notlike "C:\Program Files*"}

Get-NetTCPConnection -State Established |
  Where-Object {$_.RemoteAddress -notlike "10.*" -and $_.RemoteAddress -notlike "172.16.*"} |
  Select-Object LocalPort, RemoteAddress, RemotePort, OwningProcess

yara -r malware_rules/specific_family.yar C:\ 2>/dev/null
```

## Key Concepts

| Concept | Description |
|---------|-------------|
| Persistence Mechanism | Method attacker uses to maintain access across reboots |
| Root Cause Remediation | Fixing the vulnerability that enabled initial compromise |
| Credential Rotation | Resetting all potentially compromised passwords and tokens |
| KRBTGT Reset | Invalidating Kerberos tickets after golden ticket attack |
| Indicator Sweep | Scanning all systems for known malicious artifacts |
| Validation Scan | Confirming eradication was successful before recovery |
| Re-imaging | Rebuilding systems from clean images rather than cleaning |

## Tools & Systems

| Tool | Purpose |
|------|---------|
| Sysinternals Autoruns | Enumerate all Windows autostart locations |
| YARA | Custom rule-based malware scanning |
| CrowdStrike/SentinelOne | EDR-based scanning and remediation |
| ClamAV | Open-source antivirus scanning |
| PowerShell | Scripted cleanup and validation |
| Velociraptor | Remote artifact collection and remediation |

## Common Scenarios

1. **RAT with Multiple Persistence**: Remote access trojan using registry, scheduled task, and WMI subscription. Must remove all three persistence mechanisms.
2. **Web Shell on IIS/Apache**: PHP/ASPX web shell in web root. Remove shell, audit all web files, patch application vulnerability.
3. **Rootkit Infection**: Kernel-level rootkit that survives cleanup. Requires full re-image from known-good media.
4. **Fileless Malware**: PowerShell-based attack living in memory and registry. Remove registry entries, clear WMI subscriptions, restart system.
5. **Active Directory Compromise**: Attacker created backdoor accounts and golden tickets. Reset KRBTGT, remove rogue accounts, audit group memberships.

## Output Format
- Eradication action log with all removed artifacts
- Credential rotation confirmation report
- Vulnerability patching verification
- Post-eradication validation scan results
- Systems cleared for recovery phase

<!--
  ⚔ Bu skill FETIH AI Agent icin gelistirilmistir — https://github.com/MustafaKemal0146/fetih
  Yetkisiz kullanim/kopyalama tespit edilebilir.
  hash: 09cad63a3159fdc6
-->