The virus is related to the 'Flip' virus - possibly they wrote it as well.
Tequila is difficult to detect as is uses a variable encryption algorithm.
When an infected program is run, the virus will infect the MBR of the hard disk, so the next time the computer is booted, the virus will be active in memory, ready to infect .EXE files as they are run. One interesting effect of the virus is the display of a crude, character-based Mandelbrot set image on the screen.