Dr.Web

Dr.Web's own site, free.drweb.com, hosts and links directly to this bot, which settles any question of authenticity: this is the antivirus vendor's own product, not a third party wrapping someone else's engine. Send it a file or a suspicious link — in a private chat, or added to a group where it can watch everything shared — and it runs the file through Dr.Web Cloud, the Scanning Engine, the Link Checker, and Dr.Web's own virus-signature bases.

Being added to a group is where it earns its keep for a chat admin: it can operate in a normal mode that reports on every file and link shared, or a quiet mode that stays silent unless it actually flags a threat, which matters for a busy group where a message every time someone shares a harmless PDF would be noise. It responds in Russian, English or German, and its public profile shows over 17,000 monthly users — real, sustained usage for a security utility bot.

Because it is a genuine antivirus company's own product rather than an anonymous wrapper around a public API, it carries the strongest safety and reliability rating in this list. The trade-off with any cloud-scanning bot is the same as with a web-based virus scanner: don't send it anything containing sensitive personal data if you'd rather it never left your device, since the file is necessarily uploaded to Dr.Web's servers to be checked.