Some antivirus companies offer free versions of their software that include basic protection. These can be a good starting point for individuals looking for protection without the cost.
While you cannot have a portable real-time antivirus, you can use portable on-demand malware scanners. These are perfect for keeping on a USB drive to scan a friend's infected computer or to get a second opinion on your own system. The safest, legitimate portable scanners include: download kaspersky total security full crack portable