As predicted, hackers tried to trick users into downloading the Storm bot Trojan Friday by unleashing a flood of Fourth of July spam bearing links to malicious sites, several security companies reported.

The spam campaign, anticipated earlier in the week by MX Logic Inc. , used messages with subject headings ranging from “Amazing firework 2008” and “Celebrating Fourth of July” to “Light up the sky” and “Spectacular fireworks show,” said U.K.-based Sophos Plc. in an alert posted to the Web Friday.

Links in the spam led to hacker-controlled sites that trumpeted a video clip worth downloading. “Colorful Independence Day events have already started throughout the country,” the malicious sites claimed. “The largest firework happens on the last weekday before the Fourth of July. Unprecedented sum of money was spent on this fabulous show. If you want to see the best Independence Day firework just click on the video and run it.”

The file pitched to users was an executable: “fireworks.exe.”

Users who agreed to the download didn’t receive a video, but instead infected their Windows-running PCs with the Storm Trojan horse, which hijacked the system and added it to the existing collection of compromised computers making up the Storm botnet.

Last checked, we didn’t see any details on the Symantec web site for any cure.