Portable applications can pose a threat to information security. Users who do not have local administrator rights cannot install software on the PC, but they can bypass this restriction by taking advantage of portable applications that do not require installation. Portable applications are mobile and are stored on removable media, they often go undetected by auditing applications on the LAN. This makes it more difficult to investigate incidents related to the use of these portable applications as the information about removable media and software installed on it is often unavailable to IT security specialists.”]
Source: https://securelist.com/security-policies-portable-applications/35859/