When a program infected with Big Joke is executed, the virus will infect one previously uninfected .COM program located in the current directory. Programs infected with Big Joke will have increased in size by 1,068 bytes with the virus being located at the end of the infected file. The file's date and time in the DOS disk directory will have been updated to the current system date and time when infection occurred.
The Big Joke virus will occasionally display a message to the ser when an infected program is executed. When this message is displayed, it is written one line at a time to the center of the display. When the message completes, it will be repeated until the system is rebooted. The message text is:
"At last ...... ALIVE !!!!!
I guess your computer is infected by the Big Joke Virus. Release 4/4-91 Lucky you, this is the kind version. Be more careful while duplicating in the future. The Big Joke Virus, killer version, will strike harder. The Big Joke rules forever."
The above message's text strings can be found in files infected with Big Joke, as well as the following two additional text strings:
Big joke, in its current version, does not do anything besides replicate and display its message.
Delete the infected files.