Set-top boxes were required with some systems, but these were generic, and often in an unknowing violation of contract, former customers would donate them to thrift stores for sale or retain them indefinitely in storage when they ended their subscription to the service rather than return them to the provider.
The cable companies could send an electronic signal, called a "bullet", that would render illegal descramblers inoperative, though some were bulletproof.
To prevent this, cable providers built stronger protection against theft into new digital cable systems that were deployed beginning in the mid-1990s as part of the changeover to the new digital HDTV standard, along with assessing a large fine for the entire cost of a set-top box if the customer didn't return it upon the termination of services.
This has greatly reduced cable theft, although pirate decryption continued on some DVB-C systems that are based on the same compromised encryption schemes formerly used in satellite television broadcasting.
Most cable companies have also issued new secured outside distribution boxes that require certain keys only given out to their installers to access, making theft via outside split line more difficult.
In most modern digital cable systems the signals are encrypted, so cases of people obtaining illegal service are less common.