Rootkit

A rootkit is a type of malware designed to hide deep inside a computer's operating system or firmware, concealing itself and other malicious activity while giving an attacker ongoing control.

Rootkits get their name from root, the highest-privilege account on Unix systems. They modify core parts of a system so that ordinary tools cannot see them. Some hide files and processes, while others load before the operating system itself, making them very difficult to detect and remove.

For a small business, a rootkit means an attacker could remain inside a computer or server for a long time, quietly collecting passwords, financial information or client files. Because rootkits are built to evade detection, standard antivirus scans may report that everything is fine.

Practical tip: keep features such as Secure Boot enabled, apply firmware and operating system updates, and use endpoint detection tools that look for suspicious behaviour rather than relying only on file scanning. If a rootkit is confirmed, the safest response is usually to wipe and rebuild the affected device from trusted media, then change any passwords used on it.