What Do Trojans Do?

Trojans corrupt important files and place adware, spyware, keyloggers, and screen scrapers that can steal personal information and your online experience. They can also redirect you to fake phishing web sites—even when you type valid web addresses (URLs) into your browser.Trojan programs are most dangerous because they can create a back door into your computer that gives malicious hackers direct access to your system. Once installed, Trojans can hijack your PC and upload usernames,passwords, credit card numbers, social security numbers, and bank account numbers to specified computers for as long as they remain undetected.Hackers use chat rooms and peer-to-peer file sharing networks to target and hijack unsecured PCs. Once the Trojan opens a back door, the computer joins hordes of other "zombie" computers that the hacker can control remotely. The hacker can launch Denial of Service (DoS) attacks,generate ad traffic, send out infected software to other vulnerable computers, and pump out spam.Cyber gangs even rent networks of these zombie computers (a.k.a.bots) by the hour to other criminals for extortion and fraud. Users are rarely aware that their machines have been hijacked, since usually the only indicator is slightly slower performance.A new trend in malware is to extort money. This ransomware is a Trojan that encrypts a PC’s files or threatens to delete them one by one unless the victim pays up. After the person pays using a money transfer service, the extortionist sends them a special disarming code or decryption application.Hackers also use Trojans to exploit weaknesses in legitimate banking,online bill pay, and e-commerce sites.