Malware Detection and Removal. It's hard to tell at a glance if a computer has a virus. Only with a good updated antivirus you can know that by sure. However, there are certain symptoms that indicate the possible presence of virus (could be virus unrelated too): • Unusual slowness, without any apparent cause, may be caused by several reasons: too many applications working at same time or network problems, but also to a malware infection. • One reason you can not open certain files or programs is that has been eliminated by a virus, or you've deleted the files they needs to function. One of the most common effects of virus is missing files and folders. • Ads appearing on screen or unexpected text messages may be a clear symptom of virus infection. Generally, these notices contain unusual text (absurd, humorous, offensive, aggressive, etc). • The computer turns off suddenly for no apparent reason and restarts or crashes. Some viruses need that happening to wake up and ensure its operation, so they cause such situations. • If a program closes suddenly while we are working with it, We have reason to suspect an infection.