Hundreds of comments here:
Catalytic converter theft
Possible solution:
Catalytic Converter Theft Deterrence Lock
$this->bbcode_second_pass_quote('', 'W')hy has the CATCLAMPTM been so successful? Let’s go through the layers of protection engineered and built into the CATCLAMPTM.
The thief most likely has a battery powered reciprocating saw with one blade and 30 seconds of time to do the crime. The thief slides under the vehicle thinking it’s going to be another 30 second cash job when everything goes wrong.
First a massive, impenetrable cage made from specially designed heavy duty aircraft wire rope encases the entire converter. The wire rope is nearly impossible to cut without industrial machines. The cage has SECURITY DEVICE in very large print and the vehicles V.I.N. # is stamped on it. The cage is locked to the frame of the vehicle with the same heavy duty aircraft wire rope used to make up the cage. There is no way for the thief to get the converter out of the cage under the vehicle in a timely effortless manner. If the thief can read and has even a shred of common sense they will leave and find an easier target.
If the thief continues the quest for easy cash the thief may try to cut the CATCLAMPTM off from the converter. The special alloy collars and aircraft wire rope will destroy the blade on the saw in seconds. Frustrated and out of time the thieves will be even more likely to move on at this point.
You pay for such security though: $269.95, or $50 more for a deluxe model. Might make a good add-on option for car dealers to offer. Sounds like a solid product though.