This is a memory resident parasitic virus. It copies itself into the Interrupt Vectors Table, hooks INT 21h and writes itself to the COM files that are loaded into the memory. Depending on the version it writes itself either to the beginning or to the end of the file. Some of these viruses use commands POPA and PUSHA of 80x86 processors. "Small.108,132,149" may corrupt the files while infecting them.
"Small.122.b" contains an error and infects EXE files as COM. As a result these files halts the computer.