I also remember vividly the radio and TV ads for this brand of sweets: "Or, ee, or, *acks!" (You have to be a fan of, yes, pre-internet Tarzan movies, to connect with this ad's pitch).
Meanwhile, the (pre-internet) dictionaries defined *ack as "to cut up/dig up/chop up with heavy or irregular blows". Hence, while I never saw such a cheeky sign below, its meaning would have been clear:
There is also the more gory depiction:
But in today's Age of the Internet, the increasingly prevalent meaning of *ack is "to gain unauthorised access to data (including, say, emails) in a system or a computer". A *acker is thus like a computer software programmer; only that he is akin to a thief or mischief-maker. One variation is phone *acking. This illustration below may perhaps be helpful as a "Guide for Dummies":
Apart from *ackers, there are even *activists who claim to be (sort of) rebels with a cause. Quite a number were computer nerds who -- after acquiring notoriety -- then went on acquire respectability as university dons or infocomm CEOs or anti-*acking sleuths. You know, it takes a thief to catch a thief. Some of the stories have become legendary:
So what am I leading to? The big news (here in Singapore) since this afternoon (Nov 12):
Hmm, I wonder if there was a well-planned sting operation at work to lure those guys out, starting with PM Lee's "declaration of war". Who knows, future role-play computer games might have such titles as:
Call for *ack-tion!
Surprise *ack-ttack: Electronic Pearl Harbour!
You choose which side you are on: chenghoo (garmen) or the *ackers and/or *activists.