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Assume the installation is fully compromised. Disconnect it from every network, avoid using it to change passwords or access sensitive services, and decide whether you need forensic evidence. If malware ran as root—or you cannot prove that it did not—preserve volatile memory only when an investigation requires it, then reinstall Arch Linux from a freshly downloaded and verified official image. Recover user files selectively, rebuild system configuration, and rotate every credential that may have been present on the machine.
1. Isolate the machine before investigating
Root privileges allow malware to alter binaries, kernel modules, boot components, logs, service definitions and security tools. A process list, file listing or scanner run from the affected installation can therefore be incomplete or deliberately misleading. Containment comes before diagnosis.
- Unplug Ethernet. If the machine is wireless, disable Wi‑Fi using a hardware switch or by disconnecting the access point; do not rely on a potentially modified desktop indicator.
- Remove the host from remote-management systems, VPNs, shared storage and other trusted network segments.
- Record the time you noticed the problem, the suspected package or entry point, logged-in users, connected storage and any unusual symptoms. Write notes on a separate clean device.
- Do not log in to email, banking, source-control, cloud or administrative services from the affected host.
- Do not uninstall the suspected package, run a cleanup script or “scan” the live system before deciding whether evidence must be preserved.
If the computer is a server, isolate it at the switch, firewall or hypervisor as well as locally. Leave a replacement service or a maintenance notice in place rather than reconnecting the suspect host simply to keep it available.
2. Choose between forensic preservation and immediate rebuilding
The correct next step depends on whether evidence has legal, regulatory, insurance or business value. The Cloud Security Alliance’s 2026 response note states: “For systems where the malicious package ran as root, or where subsequent investigation cannot confirm that root privileges were absent, the system should be treated as fully compromised.” It recommends preserving volatile memory when forensic analysis is planned, then reinstalling from trusted media.
#1 Best Overall
| Situation | First action | What follows |
|---|---|---|
| Regulated data, litigation, suspected insider activity, major outage or high-value intellectual property | Keep the host isolated and contact qualified incident-response specialists. Preserve volatile memory before powering down, using a documented procedure and destination storage. | Maintain chain-of-custody notes, collect disk images as directed, and rebuild only after investigators release the system. |
| Personal workstation or non-regulated system with no need for court-quality evidence | Power it off after isolation. Prepare recovery media from a separate clean computer. | Copy only reviewed user data, wipe or re-partition the target, reinstall Arch and rotate credentials. |
| You are unsure whether root was obtained | Use the stricter path: treat root access as possible compromise. | Do not rely on package removal or a local scanner to establish trust; preserve evidence if required, otherwise reinstall. |
Memory is lost when power is removed, but leaving a compromised host running also gives an attacker time to erase evidence or reach other systems. That trade-off is why the forensic decision must be made before shutdown.
3. Prepare trusted Arch recovery media
Use a known-clean computer, not the suspect installation, for every download and verification step.
- Download the current official Arch Linux ISO and its published checksum or signature from Arch Linux.
- Verify the image against the published value before writing it. A matching checksum confirms that the file you downloaded matches the published image; signature verification provides an additional authenticity check when you use the corresponding signing key.
- Write the verified image to a dedicated USB flash drive. Arch documents USB media for installation, system maintenance and recovery.
- Label the drive, keep it under your control and store it offline when it is not needed. Do not use a recovery stick that has been plugged into the compromised host unless you have securely recreated it.
- Have separate, trusted storage ready for recovered documents. Do not use the destination disk as the only copy.
Keep a second clean computer or a printed copy of essential recovery information available. You may need documentation, password-manager access and network credentials while the old system is offline.
4. Preserve data without preserving the infection
Boot the Arch live environment from the verified USB. Treat the old installation as untrusted even if it appears normal. Where practical, mount old filesystems read-only and copy to separate storage. Avoid executing programs from the old disk.
Rank #2
Files normally worth recovering
- Documents, photographs, videos and other personal data.
- Project source code, exported databases and data files whose contents you can review.
- Mail or web-server content required for continuity, after it has been scanned from a clean system.
- Hardware information, hostnames, DNS records and boot-loader details needed to reproduce the service. Arch’s existing-Linux installation guidance specifically calls out these items, along with data and SSH keys, as information to preserve before replacement.
Files to quarantine instead of copying wholesale
| Category | Why it is risky | Safer treatment |
|---|---|---|
| Shell startup files such as profile and shell-rc files | They can run commands at every login or shell launch. | Open them as text on a clean system and recreate needed settings manually. |
| Cron jobs and systemd units | Persistence can restart malware after reboot. | Record names and schedules for investigation; recreate only entries you understand. |
| SSH private keys, agent state and known-host data | Keys may have been copied or replaced. | Do not restore private keys; generate new ones and review server authorization files. |
| Browser profiles, cookies and saved credentials | Session tokens can provide access without a password. | Export only needed bookmarks or documents; sign out and revoke sessions. |
| Package build scripts, AUR PKGBUILDs and install scripts | Build scripts execute commands with your privileges and may contain supply-chain changes. | Review every line and obtain a fresh copy before rebuilding anything. |
| Old binaries, kernel modules, unknown archives and complete configuration trees | They can contain backdoors or altered libraries. | Keep for forensic analysis only; do not place them on the new root filesystem. |
Scan recovered data from a clean, updated system before opening it. A scan can reduce risk, but it does not prove that a document, archive or source tree is harmless. Preserve the original copy separately and work from a duplicate when the data is important.
5. Reinstall Arch Linux from the trusted image
A clean reinstall is the trust reset when root execution is confirmed or cannot be ruled out. Package removal, reinstalling a few binaries or running a rootkit checker cannot establish that the old kernel, boot chain, libraries and administrator accounts are clean.
- Boot the verified Arch USB and confirm that you are operating in the live environment, not the old installation.
- Identify the target disks and partitions carefully. Disconnect unrelated disks if doing so will prevent an accidental wipe.
- Copy any last required files to separate storage. Do not proceed until the data you intend to keep exists somewhere other than the target disk.
- Partition and format the target as appropriate for the machine and your backup plan. A full wipe removes old filesystem contents; retaining an old partition without a documented reason leaves unnecessary trust questions.
- Install the base Arch system from the verified media, then configure the user account, time zone, locale, networking and storage.
- Install and configure the boot loader, and rebuild the initramfs whenever the installation procedure requires it.
- Boot the new system, fully update it, and install only the software you need. Prefer official repositories for security-sensitive components.
- Before reconnecting to production networks, enable a firewall policy appropriate to the host, confirm administrator access, and verify that backups can be read.
Do not copy the old / tree over the new one. Recreate configuration by hand or from reviewed, version-controlled files. Preserve the old disk or an image of it if investigators may later need it.
6. Understand what chroot can and cannot do
ArchWiki describes chroot as a maintenance environment used for tasks such as reinstalling a boot loader, rebuilding an initramfs and repairing packages. It requires another Linux installation or installation media and root privilege.
Chroot is appropriate when an installation is trusted but fails to boot or has a repairable package problem. It is not a disinfectant and does not prove that a compromised root filesystem is clean: commands run inside the chroot use the old files, libraries and configuration. After suspected root compromise, use the live environment to copy data and perform a replacement installation rather than chrooting into the old root to “clean” it.
7. Rotate every credential that may have touched the host
Use a separate clean device. Assume that secrets stored in memory, files, browser sessions, terminal history and configuration were readable while the malware had root.
- Change local, remote and service-account passwords, beginning with accounts that can administer other systems.
- Revoke and replace SSH keys; remove old public keys from servers and review authorized-key files.
- Invalidate API tokens, cloud credentials, deploy tokens, registry credentials, signing keys and automation secrets.
- Revoke browser sessions and refresh tokens; change passwords after sessions are invalidated.
- Rotate database passwords, VPN credentials, backup credentials and any secrets in environment files.
- Review authentication logs from a separate system for unexpected logins, key use, new accounts and privilege changes.
Generate new keys on the rebuilt installation only after it is updated and protected. Do not restore private keys merely because they were convenient to copy.
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8. Restore services and files selectively
Restore in dependency order: identity and administration, storage, core services, application data, then user-facing applications. After each stage, test from another machine and record what changed.
Rank #4
| Restore source | Decision | Checks before use |
|---|---|---|
| Offline backup made before the incident | Preferred source, provided its date and integrity are known. | Scan it on a clean system, compare expected file types and review recent changes. |
| Version-controlled configuration | Use when commits are reviewed and the repository was not writable by the compromised host. | Inspect commits around the suspected compromise and regenerate secrets outside the repository. |
| Files copied from the old disk after compromise | Use only for necessary user data. | Keep originals isolated, scan working copies and never restore executable system files automatically. |
| Old root filesystem image | Retain for investigation, not routine restoration. | Mount read-only for reference; rebuild required settings manually. |
For databases, export logical data from a clean environment where possible instead of restoring an entire compromised data directory. For websites and applications, inspect templates, plugins, uploads and deployment scripts for altered code before publishing them.
9. Review the AUR and package provenance
Arch’s June 12, 2026 notice reported a high volume of malicious AUR package adoptions and updates and urged users to review PKGBUILD and install-script changes. The Cloud Security Alliance’s 2026 note describes an AUR supply-chain campaign involving rootkit concealment. If an AUR package may have executed as root, a clean reinstall is the appropriate trust reset.
Before installing an AUR package on the rebuilt system:
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- Read the complete PKGBUILD and every referenced install script, including changes since the last version you used.
- Check the source URLs, checksums, maintainer history and package contents.
- Build in a disposable environment when practical and inspect the resulting files before installation.
- Prefer an official repository package when it provides the required security-sensitive component.
- Keep an inventory of installed packages, their source repository and the date each was approved.
| Source | Strength | Operational caution |
|---|---|---|
| Official Arch repositories | Centralized publication and documented package metadata. | Still update promptly and verify that the package meets your configuration needs. |
| AUR | Broad software selection and community-maintained build recipes. | PKGBUILDs and install scripts require your review; do not assume community status means automatic trust. |
10. Harden the rebuilt installation and prepare for the next incident
- Apply all available system and firmware updates before exposing the host to untrusted networks.
- Use separate, least-privilege accounts for daily work and administration.
- Restrict SSH, disable unused services and require strong authentication appropriate to the environment.
- Keep an offline or otherwise isolated backup with regular restore tests. ArchWiki notes that backups enable recovery from ransomware, data corruption, accidental deletion and system compromise.
- Maintain a package inventory, AUR review notes, hardware details, hostnames, DNS information and boot-loader configuration.
- Keep a verified rescue USB and a second copy of essential recovery instructions.
- Centralize logs on another system when the host’s logs are important for detection or investigation.
- Alert on new privileged accounts, unexpected services, changes to boot files and unusual outbound connections.
Common mistakes and recovery branches
“I removed the malicious AUR package. Is that enough?”
No. Once code has run as root, it may have modified the kernel, boot loader, libraries, credentials and logging. Removal addresses one package name, not every possible persistence mechanism. Reinstall when root compromise is confirmed or cannot be excluded.
“The live USB cannot see my disk.”
Stop before changing partition data. Check that the USB itself was written from a verified image, confirm the correct storage device and investigate firmware, controller or encryption requirements from a clean environment. If the disk is failing, make a forensic or recovery image before repeated repair attempts.
“I need files from an encrypted or damaged filesystem.”
Do not repeatedly mount it read-write. Preserve the original, use a separate destination and obtain specialist help when the data is irreplaceable or evidence may matter.
“I restored a backup and the symptoms returned.”
Disconnect the host again. Identify the exact backup set and restore point, inspect scheduled tasks and application code, rotate credentials once more, and rebuild from a known-good backup rather than layering repairs onto the suspect installation.
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Keep the compromised host isolated and bring up a separately built replacement from trusted media or a known-good image. Preserve the original for responders instead of reconnecting it to production.
Quick Recap
Recovery checklist
- Network disconnected and remote-management access removed.
- Incident time, suspected entry point and affected services recorded.
- Forensic requirement decided before shutdown; volatile memory preserved when required.
- Official Arch ISO downloaded and checksum or signature verified on a clean computer.
- Recovery USB and separate destination storage prepared.
- Only reviewed user data copied; old root filesystem, startup files, units, keys and binaries quarantined.
- Target disk wiped or re-partitioned and Arch installed from trusted media.
- System updated, boot chain rebuilt and unnecessary services disabled.
- Passwords, SSH keys, tokens, API credentials and sessions rotated from a clean device.
- Backups, package inventory and rescue media confirmed before normal use.
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