Caller ID Spoofing
Another relatively simple method of phone hacking is to use a spoofing servicethat makes it appear as if the hacker is calling from the phone he or she is trying to break into. As a convenience feature, many phone mail services allow you to avoid having to type in a PIN every time you check your mail as long as you call from your own phone. But these easy to find spoofing services can make it look as if the hacker is calling from your phone so rule number two is to make sure your phone requires a PIN each time you check your voice mail.
There is also the possibility of malware being used to infect a smart phone. There have been cases of malware on Android phones that give the attacker complete control over the phone, so it is quite possible for a piece of malicious software to access your voicemail as well as your contact list, calendar or even your physical location.
I’m not sure what to say about social engineering since most cases involve the hacker calling the phone company and posing as the subscriber. We have a right to expect that companies have good security processes in place which make it possible for legitimate users to recover a password or PIN without making it possible for unauthorized access. Companies need to use positive measures to make sure they’re speaking with the right persona and use extra precautions such as sending the PIN # to the phone itself (via text) so that — at the very least — you have to have physical possession of the phone to get the information.
Avoid secrets on your phone
Finally, it’s a good idea to encourage people not to leave highly confidential messages on your phone. Sure you have the right to privacy but, unfortunately, if someone is determined to break into your voice mail, there are ways to do it despite your efforts to stop them. So, as a precaution, don’t use cell phones for secret communications or messages.