In 2005, the Federal Trade Commission, the Department of Commerce, the Department of Homeland Security and 33 other agencies from over 20 countries launched Operation Spam Zombies to fight against spam — specifically targeting "zombie" machines that were responsible for sending millions of junk e-mails each day. It began by sending letters to over 3,000 ISPs worldwide, instructing them on how to prevent customers' computers from being compromised by spammers. In July, the next phase of the operation began, identifying spam zombies and directly notify networks that are hosting them.