Police charged the 24-year-old Point Clare man, whose name was withheld, with two counts of unauthorized modification of data to cause impairment and one count of unauthorized access to, or modification of, restricted data, a release from the Australian Federal Police said.
The alleged hacker is an IT professional employed at a company where he had access to sensitive information about clients, including various government agencies, the release said.
The specific way in which the man allegedly defaced the website and which government agency was targeted was not reported.
The Cyber Crime Operations investigators said they were tipped off to his alleged actions when they found a government website compromised. The man is the first member of Lulzsec to be charged by federal police.
"Those thinking of engaging in such activities should be warned that hacking, creating or propagating malicious viruses or participating in distributed denial of service attacks are not harmless fun," said Cmdr. Glen McEwan, manager of Cyber Crime Operations. "Criminal acts such as this can result in serious long-term consequences for individuals, such as criminal convictions or imprisonment."
The suspect was released on bail and is scheduled to appear in Woy Woy local court May 15, police said.
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