Sites pretending to be official web sites to either obtain your sensitive information or trick you into downloading and running a malicious file.
False pop-up claiming that your computer is infected.
False updates for your applications or system.
Phishing emails with false links requesting access to personal or financial information.
USB drives and other external media
Infected USB or flash media automatically running malicious applications when autorun or autoplay is enabled. USB drives and flash media must first receive the infection from an infected machine for this to occur.
Phone calls from alleged helplines
A caller claiming to be from a well known company, like Microsoft, saying that fatal errors on your system must be fixed immediately and asking you to give remote access to him/her after which he/she will install malicious programs.