Hackers infected computers, derailed websites, and plundered networks in a memorably miserable quarter, according to a report released Wednesday by Internet security firm PandaLabs.

Hacking groups Lulz Security and Anonymous caused "widespread mayhem" during the three months ending June 30, and malicious software "spread substantially," according to the research unit of Spain-based Panda Security.

"This quarter has been one of the worst on record," PandaLabs said in a quarterly security report.

"The number of attacks suffered by businesses and large organizations has set alarm bells ringing as systems and companies that until now were considered 'hack-proof' have fallen victim to cyber-crime," the report continued.

Hacking victims have ranged from the International Monetary Fund and the US Defense Department to Sony, SEGA and Citigroup.

While computer networks were cracked for motivations apparently political, financial, or mischievous there was a significant spread of viruses to computers in homes around the world, according to PandaLabs.

Hackers can seize control of infected computers and use them to attack networks or websites.

Researchers determined that an average of 42 new strains of malicious software, referred to as "malware," were created each minute during the recently-ended quarter.

A list of countries with the greatest infection rates was topped by China, where PandaLabs estimated that 61.33 percent of all computers were tainted with malware.

Thailand placed second with 56.67 percent and Taiwan third with 52.92 percent, according to PandaLabs.

The United States and much of Europe was ranked near the global average of 39.79 percent.

Sweden was said to have the lowest incidence of malware infections at 27.29 percent, followed by Switzerland and Norway which both had fractions more than 29 percent.

The findings were based on data from a Panda ActiveScan online tool that people can use on-demand to check computers for viruses.

The quarter also revealed blurred lines between online activism, or "hacktivism," and criminal cyberattacks.

"It seems that the only way the Anonymous group has to protest is by committing illegal acts," the report stated.

Hacker collective Lulz Security, or LulzSec, rampaged the Internet with a stated mission of simply having fun at the expense of others.

"If you took the most irresponsible and brainless members of Anonymous and put them all together, they would be considered the most refined gentlemen compared to LulzSec," the report concluded.

LulzSec said on June 26 that it has ended an Internet rampage that included cyberattacks on videogame companies, police and even the CIA's website.

"For the past 50 days, we've been disrupting and exposing corporations, governments, often the general population itself, and quite possibly everything in between, just because we could," the group said in an online farewell.

"It is time to say bon voyage," the message concluded. "We must now sail into the distance."

While it remained to be seen whether members of the group would truly stop bedeviling the Internet, it was unlikely police would abandon efforts to track them down.

In the days before its farewell message, the group released hundreds of documents from the Arizona Department of Public Safety.

The documents included information on drug cartels, street gangs, informants, border patrol operations and the names and addresses of members of the Arizona Highway Patrol.