Anvi Smart Defender is a full-featured antivirus tool which also includes multiple PC optimisation tools to clean and speed up your system.
The program offers three on-demand scan types - Quick, Full and Custom - all of which work quickly, although at first glance we're unconvinced of its accuracy.
A Cloud Security option enables you to drop a suspect file directly onto the program for a speedy analysis and verdict.
Real-time protection checks your startup programs, running processes and the files you access, while also monitoring program behaviour to detect and remove malware before it can do any harm.
A set of PC maintenance tools include hard drive and Registry cleaners, a disk defragger, a privacy tool to clear your internet tracks, and more. These aren't particularly thorough, but they are at least fast, completing in just a few seconds on our test system.
And most conveniently, the authors claim Anvi Smart Defender is "Compatible with All Antivirus Products", so you should be able to run it alongside your existing security tool. We installed both Anvi Smart Defender and Norton Internet Security 2012 on our test PC to check this, and didn't notice any conflicts; Smart Defender was fast, hassle-free and lightweight, typically requiring under 4MB of RAM when running in the background.