Phishing is the fraudulent act of obtaining information through email or instant messaging by falsely claiming to be a trusted source. 
The message will usually alert you to a fake problem and offer to fix it by asking for your bank account information, PINs, or password. Some of these attempts are very realistic in appearance and may even direct you to a familiar looking website. It is a good rule of thumb to never respond to any emails of this nature, regardless how valid they may appear. Call your credit card company, IT administrator, help desk, etc., if you doubt the validity of a message.
What is the difference between a worm, virus, and trojan? | Stratepedia Blog | June 10th, 2010
[...] Trojan horse, also known as phishing, spreads quickly and does the most harm by posing as a trusted website, link, software, [...]