Spammed malware activity boomed during the month of July, according to Google.

The company's Postini security branch recorded a major spike in malicious spam traffic over the month, peaking at 10 million messages logged on 24 July.

The numbers are the highest recorded all year. Previous spikes logged by the company in March and April had only reached numbers of approximately four million.

One of the prime offenders cited for the spike was an attack centred around fake UPS invoices. The user was asked to download malware disguised as software to track the supposed parcel.

Also cited was the wave of attacks touting phony news articles. Attackers sent out spam messages containing links to supposed news sites. When the user visited the fake site and attempted to watch a movie file, the malware was installed.

"Many of the viruses we see follow a similar format, in which an email with an embedded web site link in the message is changed from what the link displays, " wrote Google Apps security and appliance team member Amanda Kleha. "The majority of the links were valid, but there were some that were replaced with malicious links."

Kleha noted that the spike follows a general pattern in which spam volumes increase over the summer. Google predicts that the flow of spam will remain high through August as spammers continue to look for new methods of spreading malware.

"On 5 August, we saw a large inflow of messages with an encrypted .RAR attachment," she said. "The overall 2008 trend has been a decrease in the use of attachments, so this new virus is confirmation that spam doesn't follow trends for long."