Portable antivirus is generally used by users who want to quickly scan a system before using it (like libraries and internet cafes). It's also used to find malware and suspicious programs on a heavily infected computer. Since you can't install a traditional antivirus on an infected system, these portable antivirus programs help you find the root issue and allow you to remove them without even turning on the system.
Kaspersky portable antivirus applications are considered as one of the "must-have" programs for any computer. They help in securing your PC (and the data on it) against avast portable antivirus for usb all kinds of viruses, spyware, and other malicious software.