Your EFTPOS unit can be skimmed in seconds, I have seen a video of two people skimming a unit in less time then it took you to read this, they skimmed a unit. If they had succeeded everyone who in that shop uses their EFTPOS on that unit will have their card details and pin numbers recorded by the thieves. The merchant would have probably spent the next few years in court and it would be expensive. Studies show most small businesses do not survive long a major skim.
It's a worry, in a recent discussion that I attended, we talked about this matter of EFTPOS security. I could not get an overall answer as few EFTPOS providers handle the units themselves as this is generally subcontracted. You really need to talk to your EFTPOS provider to find out, however, I could get an answer out of Tyro because they do not subcontract this out.
There is a series of systems in place to protect against these attacks although they do occur.
Sometimes they can be detected by the terminals. Tyro has a system of tamper resistance built-in. In the event the unit detects any hardware tampering; they will refuse to perform any transactions.
Depending on the type of attack, the terminals if it picks it up will display one of several messages, but generally, you would get something like this.
If this happens, the unit will no longer work and will need to be replaced.
now if you notice they are curved everywhere part of the reason for this is to prevent skimming hardware from being attached on top of this unit. Still you cannot be too careful.
Three tips that I do recommend you consider is
1) Use a highlighter and writing something like "Property of West Footscray Gift Shop" around on the EFTPOS unit. It just makes it harder for the skimmer to put his unit on top of yours as they need to duplicate your writing too.
2) Run your hand around the unit and make sure that there is nothing on it. I do that before I put any card on a terminal.
3) If you have an old EFTPOS unit, get it replaced, Tyro users can do this free of charge. They are just too dangerous these old units.