I sometimes like to check spam just to see how the messages look like, and I found someone who actually put an American phone number (1-XXX-XXX-XXXX). Most of these spammers are either trying to get money out of you, or hack you in ways like disguising as services like Google+.

Not that I actually want to, but I am curious if calling the number would do something to my phone. How could a hacker possibly access sensitive information just by tricking someone into calling. I have heard (no idea where), that some numbers when called, will charge you an enormous bill. Could this be true?

Can you get "hacked" by calling a number?


  I am curious if calling the number would do something to my phone. How could a hacker possibly access sensitive information just by tricking someone into calling. 


It could be a hack, or it could be a prelude to a hack. Here are some rough examples:


If you call them, the spammer can find out if that phone number is owned by an actual person. The spammer can also easily fake the same area code as you, and set up a clever social engineering trick that may involve you thinking with the wrong head.
If you're dumb enough to call them, you may be gullible enough to fork over additional information. If you're dumb enough, they may call you from other numbers, or forward you to another number.
There may also be an exploit in your phone's processing of various messages/content types. While they could easily target all phones at once by using some form of auto-messaging feature, this may be easily stopped by carriers. 


Learning more about you allows an attacker to guess secret answers, passwords, etc. If you're the gullible type, chances are you don't have a good password policy, or you could be tricked into visiting a malicious website, or both.



But why not just send infected videos or pictures to everyone?

Let's assume the spammer has developed, or found, a program that helps with automatically dialing phone numbers.

If they're sending an infected video or picture to multiple recipients, they may quickly run out of data. It's far cheaper and easier to target people individually, especially those gullible enough to call the number. 

In fact, if they target everyone, then that also increases the chance of their scam becoming well-known. By limiting their attacks only to the gullible, they've found a very good way to limit detection and knowledge of their particular scam.

The reason why they'd want to limit knowledge is that many folks may be searching for a particular scam, not exactly their specific scam. This is a problem with many gullible people: they can't really think outside the box, and not realize it's the same type of scam, but with different features. 



Your information helps scammers engage in Social Engineering tactics

Have you ever tried to contact customer service for anything important, such as banks, online game accounts, websites, etc? Usually, they need specific information from you, or someone pretending to be you, in order to handle your request.

In fact, just recently, I was able to social-engineer a customer service representative for an account of mine by providing details on things I knew about me, without actually providing any real concrete details, or even providing my identity. All I needed was a few bits of information about myself.

Social Engineering is a tactic used everywhere, and often results in  astounding success because people in general are ill-equipped to handle it. If a spammer has your phone number, then it may be possible for them to get other information. Maybe your phone number is tied to different accounts. 

Maybe they have a partial database of credentials stolen from various websites, which could include more information on you. Maybe that database includes information on your email address, which will allow the scammer to continue their campaign of phishing without you realizing it.



Can calling spam numbers cost me money?


  I have heard (no idea where), that some numbers when called, will charge you an enormous bill. Could this be true?


Yes, this is possible. 

If you're calling a premium-rate telephone number, then that could cost you a lot of money when you call them. If you text a number associated with a "donation", whether it's legitimate or a scam, your phone bill will likely include additional charges.
