upx -t program.exe (Checks the integrity of the packed file). Important Security Note UPX: the Ultimate Packer for eXecutables - Homepage
Smaller files mean faster downloads and lower bandwidth costs for developers. download latest version of upx
To ensure you are getting a secure, unmodified version of the software, you should only download from official channels: upx -t program
Because of its efficient decompression algorithms, there is usually no performance penalty when the program starts up. How to Use UPX (Quick Start) unmodified version of the software