At first glance it is just another printer; one of those big machines that sits against the wall of thousands of offices around the country, turning blank sheets of paper into corporate documentation. And as inoffensive as it may seem, just another piece of office furniture, it can become a threat to your company’s confidentiality. While your printers and networks can become one your most vulnerable security holes, the one created by the ‘hacker’ Julian Oliver is quite simply a spy.

Every time you make a call on your cell phone, the device connects to the nearest phone antenna. What Oliver has managed to do is to camouflage a similar antenna inside an everyday office printer.

In this way, the device can intercept all calls made or received from an office, thereby allowing an attacker to spy on conversations or read SMS messages.

In this case, however, there is nothing to be afraid of. This has simply been an experiment through which Oliver has tried to draw attention to the importance of using communication tools with end-to-end encryption, such as the Signal messaging app recommended by Edward Snowden himself.

Yet the fact that is only a demo shouldn’t detract from the lesson to be learnt. In the strategy used by Oliver, every time a phone connects to the antenna camouflaged in the printer, the device sends an SMS. If the recipient responds to any of these messages from an unknown number, the printer prints the SMS message and the ‘victim’s’ phone number, thereby revealing the scam.

What’s more, the printer is programmed to make calls to the phones that connect to its antenna. If someone answers, all they will hear is a Stevie Wonder song. A practical joke that lasts some five minutes; after this time, the printer disconnects the phone from the antenna, allowing it to connect to the genuine mobile network. In the event of a real attack however, the consequences won’t be as entertaining, nor the scare so brief.

Oliver’s experiment serves to remind us of the fragility and vulnerability of the communication networks we use every day. A simple Raspberry Pi motherboard and two GSM antennas would be enough to enable an attacker to camouflage an antenna in a printer and spy on all of a company’s phone conversations and steal confidential corporate information.