it is not a anti-virus actualy, but is some kind of new security product, and it is the best in china among the same kind of product.
buit-in with 4 anti-virus engine which is
1) 360 cloud antivirus engine
2) 360 heuristic engine
3) 360 QVM engine (some kind of another heuristic engine) (choose to open)
4) Avira antivirus engine (choose to open)
(NO.2-4 just use for scaning, not in real time protection, so it will not affects your system's performance even so many engine buit-in)

anyway, don worry for real-time protection. 360CLOUD HIPS was used to replace the real time protection.

360安全卫士(360 safeguard) is the main product from QIHOO.
360杀毒（360 anti-virus) is minor, however, 360anti virus get a good result in many kind of antivirus test, such as av-c, vb100, av test, westcoast....
360safeguard is very rely on their cloud technology, so i will just recommend this product if your computer is always connected to the internet.

If your computer is in good or avarage spec, 360antivirus + 360 safeguard is recommended.
anyway, if your compter is really low spec, just install 360 safeguard is enough.

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Added on March 2, 2012, 1:32 pm

This 360 is an anti-virus la. It is a China made product. This software has a very small foot print. Its basic functionality is there and allow u to install added components any time. The good thing is it is small and fast. The bad thing is it allows a lot of China based spyware/ malware based movie downloading programs to work. Most of the time it allows them to to pass. If any of you have used any d/l software made by China, almost all of them are flagged with some trojan and virus with a scan by malwarebytes which is not an antivirus software.

But 360 has improve somewhat. And do read the news that any China made software has codes included by their goverment to monitor usage. Communism at work here.