Leetaru and Althaus discovered the changed press releases by comparing them to copies at the Internet Archive, an organization that takes snapshots of the Web for posterity.
Brewster Kahle, director and co-founder of the Internet Archive, describes the site as a library for the digital age, a place where information is kept. That may seem unnecessary, but according to Kahle, "the average life of a Web page is 100 days."
Kahle finds the report by Leetraru and Althaus to be troubling. "If people are allowed to change past to suit the present, we're living in an Orwellian world," he said.
Yet even he acknowledges that some flux in the historical record is necessary. "We've never had pressure to change things [in our archive], but do respond to people wanting to take things out of the Wayback Machine," he said, noting that not everything published online is intended to be preserved.
Kahle concurs that technology has made it harder to revise history, but only in certain circumstances. "For spectacular things, it's hard to take things off the Net," he said. "But in general, things are going away much more rapidly than they did in the past. All in all, we’re seeing information disappear as the ground changes."
There's an opportunity here, Leetaru suggests, for a company to apply the third-party certification authority model, practiced by VeriSign as the certifier of SSL certificates, to public document integrity.
"Government agencies like the White House and even companies that have documents they want to show have been unaltered (such as electronic legal contracts) would pay to have this service create MD5 fingerprints of their documents and store them," said Leetaru in an e-mail. "The company would offer a browser toolbar with an 'authenticated browsing mode' where the browser automatically computes in the background an MD5 hash for each page the user visits and compares it against the MD5 hash stored on the company's site to verify that the page has remained unchanged, much in the way Google's toolbar offers a phishing alert to warn of potentially unsafe Web pages."
"By making the verification process more transparent and automatic, verifying whether documents are original or not will become just a normal part of the Web browsing experience, rather than a labor-intensive effort in digital forensics," he said.