While there are an infinite number of social engineering exploits, typical ones include the following:
Stealing passwords: In this common manoeuvre, the hacker uses information from a social networking profile to guess a victim's password reminder question. This technique was used to hack Twitter and break into Sarah Palin's email.
Friending: In this scenario, a hacker gains the trust of an individual or group and then gets them to click on links or attachments that contain malware that introduces a threat, such as the ability to exploit a weakness in a corporate system. For example, says Netragard CTO Adriel Desautels, he might strike up an online conversation about fishing and then send a photo of a boat he's thinking of buying.
Impersonation/social network squatting: In this case, the hacker tweets you, friends you or otherwise contacts you online using the name of someone you know. Then he asks you to do him a favour, like sending him a spreadsheet or giving him data from "the office". "Anything you see on a computer system can be spoofed or manipulated or augmented by a hacker," says Desautels.
Posing as an insider: Imagine all the information you could extract from an unknowing employee if you posed as an IT help desk worker or contractor. "Roughly 90% of the people we've successfully exploited during [vulnerability assessments for clients] trusted us because they thought we worked for the same company as them," Desautels says.
On the Netragard blog, he describes an exploit in which a Netragard worker posed as a contractor, befriended a group of the client's workers and set up a successful phishing scheme through which he gleaned employee credentials, eventually gaining entry to the entire corporate infrastructure.