I went with 'Civil Defense' as well. It really addressed something which was in the shows bible but rarely featured. Star Fleet had taken control of an ALIEN space station and was trying to use unfamiliar equipment at times. With control freaks like the Cardassians it is not surprising to have hidden control programs.
The Phaser unit appearing in replicators is brilliant! Check for concealed weapons all you want, the computer will create and fire them when it wants to. Having Dukat strolling through the beams was funny as hell and the look on his face when the program decided he was also part of the problem and removed his authority was priceless.
The only downer was having the massive destruction overload just turn into a light show at the end. After all that buildup they should have had some significant damage at least (to be spotlessly repaired before the next show of course)