A full scan is a deeper antivirus or endpoint security check than a quick scan. It usually starts by checking memory and active processes, then continues through mounted fixed disks and, if configured, removable or network drives. Because it examines more files and locations, it takes longer but can find dormant malware that is not currently running.
In cyber security, full scans matter as a verification tool. Defenders use them to look for hidden executables, suspicious scripts, persistence mechanisms, and file-based threats that may evade a fast check. Attackers try to survive these scans by using encryption, packing, rootkits, or living-off-the-land techniques that leave fewer obvious files behind. A failed or interrupted full scan is also a useful signal for defenders, because it may indicate a product problem, a policy issue, or a deeper stability issue in the scanning engine.