The short answer is maybe, but probably not. Antivirus software scans files and programs to ensure there is no malware or other harmful threat present. The longer the time frame between each scan, the more files the program will need to check. These intensive scans may have some noticeable effect on your computer speed. It's therefore recommended that you schedule your scans to run more frequently and/or at night so as to not impact your computer usage. While antivirus software can affect the speed of your computer, it is most likely not the only factor—or even the most prominent. Other factors such as unnecessary startup and background programs, insufficient RAM, or even undiagnosed malware can have more drastic effects on your computer speed than a simple antivirus scan.