A security firm revealed that even "smart" appliances are vulnerable to hack attacks. A group of cybercriminals have used a "smart" refrigerator to send 750,000 spam emails.

Smart appliances are household devices that are able to connect to the Internet including computers, home Internet routers, media PCs and smart TVs. These devices can communicate to the smartphone, tablet or laptop through Wi-Fi. One example is a "smart" refrigerator which can tell the owner when it's time to change the filter. This new technology was designed to simplify tasks at home and save energy costs. However, since these appliances are able to connect to the Internet, it makes sense that cybercriminals were able to find a way to exploit them.

A report from U.S security firm Proofpoint Inc. revealed that cybercriminals have hacked over 100,000 smart appliances and used them to send out more than 750,000 spam emails across the globe. Just imagine your refrigerator sending an email to your smartphone, laptop, or tablet.

David Knight, general manager of Proofpoint's Information Security division, said in a press release, "Botnets are already a major security concern and the emergence of thingbots may make the situation much worse."

 "Many of these devices are poorly protected at best and consumers have virtually no way to detect or fix infections when they do occur. Enterprises may find distributed attacks increasing as more and more of these devices come on-line and attackers find additional ways to exploit them," he added.

The hack attack allegedly happened between December 23, 2013 and January 6, 2014, three times a day. Proofpoint reported 25 percent of the spam emails sent to both personal and business email addresses were from smart appliances.

The security firm also noted that the hacker behind this attack is difficult to trace location-wise because several IPs were used.