Hi mattytun1514
There are several free antiviruses available in the android market (Market application comes preinstalled on galaxy s2) like: Anti-Virus Free (AVG), Anti-Virus Pro (AVG-trial), McAfee Mobile Security, McAfee WaveSecure, McAfee Family Protection (if you've got little kids using your phone), Norton Mobile Security, BitDefender Mobile Security etc .
I have installed BitDefender Mobile Security on my missis Galaxy S II. I have never used it before, but BitDefender is the #1 PC antivirus for this year. So I thought it might be the best mobile phone antivirus as well. It works smoothly, doesn't slow down her galaxy s2 (she has around 100 applications on the phone: default apps, email apps, chatting apps, games, news, audio/ video players, remote connection, converters, etc) and it scans every single application that is download. Full malware scanning takes less than 30 seconds!
From bamz