The free version of Avira Antivirus is among the most popular.

查杀病毒的免费版本是最流行的。

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Free anti virus products are available from known companies such as AVG, Avira, Panda Software, or Trend Micro.

FORBES: IBM Distributes Malware-Infected USB Sticks At Security Conference

In the free software market Microsoft faces competition from many others including AVG, Alwil Avast, Avira Antivir and Comodo.

BBC: Microsoft launches free security