PopupSpo is a cookie.
Cookies are small text files stored in the browser on the user's computer, when visiting web pages.
Cookies store information that can be used for several purposes: to personalize web browsing, to gather demographic information about how many users visit a page, to monitor which banners are displayed to the user, etc.
These uses are not, in theory at least, malicious.
PopupSpo prevents access from programs to websites of several companies related with security tools (antivirus programs, firewalls, etc.).
PopupSpo redirects attempts to access web pages of certain banks to spoofed pages, with the aim of logging information entered by the user in these pages.
PopupSpo redirects attempts to access several web pages to a specific IP address.
PopupSpo does not spread automatically using its own means. It needs an attacking user's intervention in order to reach the affected computer. The means of transmission used include, among others, floppy disks, CD-ROMs, email messages with attached files, Internet downloads, FTP, IRC channels, peer-to-peer (P2P) file sharing networks, etc.