If you feel you need one, there are several free anti-malware apps available on the markets. I'm using Lookout on mine with no apparent performance issues. Another popular one is AVG Antivirus Free.
Been using Lookout for several years, first on my Android phone. One of the first apps I downloaded to my Nexus 7 when I got it. There is some unused functionality of the app on the tablet because those functions are for phones connected to a carrier, but for basic anti-virus / malware, it still does the job and is free!
I recomand Avast. I used Avast for Win for about 2 year at home and work and I don't have any problems. I see now a version for android, but it isn't available on Market Play. Google search on net and download. I used free version. I will test (android ver.) and I will post observations.
as a Linux user I never seen the use of an anti-virus really that necessary.it just takes up ram usage.android,being based on the Linux kernel,is Linux.viruses don't stick to the os.only passable if transferring to a windows os.ive never used antivirus on any android devices and I do fine.i do install a lot of apps from blackmart and such.the only leak is a Trojan app that invades all your info off your device.look for it when installing apps, it usually says "WIFIADAPT." then again a lot of apps ask for permissions for a lot of unnecessary details off your device.my answer for antivirus would be that it is not recommended,just optional.a lot of people don't understand the open-source concept.remember it is not windows.