ClamAV, a widely adopted free and open-source antivirus software developed by Cisco Talos, will undergo a substantial cleanup of its signature databases in December, marking its largest reduction effort since the project began more than two decades ago.

Cisco Talos, which maintains ClamAV, has evaluated the full signature set and identified large numbers of entries that no longer match any activity in current threat data. These signatures will be retired beginning December 16, 2025, resulting in smaller databases and lower resource usage for users.

The change will have an immediate and measurable impact. The main.cvd file, currently around 163 MB, will shrink to roughly 80 MB. The daily.cvd file, which is 62 MB today, will fall to about 22 MB, so that users will see it is nearly half their current size.