Glenn Mangham of York, England, said he meant no harm and hoped Facebook would let him off the hook.
The hacker who stole Facebook's source code has gone public with a deeper explanation of how he penetrated the world's most popular social network.
Glenn Mangham, of York, England, posted a lengthy writeup on his blog and a video, saying that he accepts full responsibility for his actions and that he did not think through the potential ramifications.
"Strictly speaking what I did broke the law because at the time and subsequently it was not authorized," Mangham wrote. "I was working under the premise that sometimes it is better to seek forgiveness than to ask permission."
Mangham implied he meant to contact Facebook once he had noticed the social-networking site had observed his intrusions, which he did little to hide. He didn't use proxy servers because he said it made auditing take longer due to the time delay between each request made to a server. He was also hoping that even when he got caught, Facebook would let him off the hook.
That didn't happen. He was charged and eventually pleaded guilty to three counts of unauthorized access to computer material and unauthorized modification of computer data, according to The Press newspaper in York.
Mangham was sentenced to eight months in prison in February, but the sentence was reduced to four months by an appeals court earlier this month. He was then eligible for release, subject to electronic monitoring and restrictions on his internet use.
Mangham used a vulnerability to download Facebook's source code, arguably the company's most valued and secret intellectual property.
Mangham portrayed himself as a security researcher who continued to probe Facebook because he wanted to look deeper for other security issues, since most systems have "a tough outer shell and a soft inside." He wrote that in the past he had been paid by Yahoo for finding vulnerabilities.
He said he took steps to prevent damage to Facebook's systems, hard-coding a delay in scripts he used to extract the source code to prevent "throttling of the server and impeding its availability."
After he knew Facebook was on his trail, Mangham wrote he "panicked because I knew how bad it looked without sufficient context." He maintained that "almost nobody" knew he had a copy of the site's source code, and that he kept it "physically detached from the internet."
"In many respects, it was better secured than the original," Mangham wrote.
Mangham's copy of the source code would surely have been of interest to cybercriminals who attempt to use Facebook to perpetuate scams. But he wrote he had no intention of selling the code.
"It is also worth mentioning that I had the source code for just over three weeks with absolutely nothing to prevent me from making copies and redistributing it, this was more than enough time to have caused significant damage to Facebook or to find a buyer, if that had ever actually been my intention but quite clearly it was not," Mangham wrote.
"When you consider that the only thing that stood between Facebook and potential annihilation were my ethics then I think the fact that it's all still in good working order should serve as some proof that I'm really not one of the bad guys," he wrote.