Auckland company Computer Forensics took about 30 hours to uncover government and commercial data on three PCs which, according to the company that sold them, should not have been there.
Ark Recycling, which supplies second-hand PCs primarily to schools, uses a process called zeroing, which is supposed to overwrite all data with zeros.
The PCs bought by Computerworld apparently hadn't undergone that treatment, says Ark director Bob Lye.
Even so, Computer Forensics managing director Brian Eardley-Wilmot (pictured) says there are widespread misconceptions about the efficacy of reformatting disks and deleting files as a means of erasing data. Such methods leave data intact, he says, for organisations like his to uncover with analysis software.
And just because a file has been overwritten once doesn't mean there aren't temporary versions still to be uncovered.
Eardley-Wilmot says PCs can be made safe for disposal if the owners make the effort to overwrite data using a tool like WipePro. He says the process is painstaking, requiring that every part of every sector be written to. And he believes few organisations do so.
"The culpability starts with the owner of the information," Eardley-Wilmot says.
Two of the PCs he analysed for Computerworld contained files relating to the activities of government agencies; the third appeared to have been owned by finance company AVCO, which was bought last year by GE Finance.