Here in Brazil this anime was on air by Cartoon Network and it's called Corrector Yui (Yui is the one in pink). And yes, she fights viruses in the cyberworld. It's a cute anime!

This is so cute... it could almost be used as a super power! Isn't this that manga... um... what was it called again? She enters the cyberworld to fight viruses and such... um... anywho, cool!