An anonymous reader writes "Last week Slashdot reported on the blockage
of a union website by Telus, a leading Canadian ISP. Since
that story, the company has restored access but the fallout
continues. The move may lead to new
ISP regulations in Canada and a study
by the OpenNet Initiative has found that by blocking the union
site, Telus also blocked an additional 766 websites including a breast
cancer fundraising site."
From the article: "While there are a number of different ways to block access to Web
sites, the method Telus chose to block the Voices for Change site --
blocking its IP address -- produced massive collateral filtering.
Filtering by IP address is efficient since ISPs can quickly and
effectively block access to the target site using their existing routing
technology. Many ISPs already block certain IP addresses to combat
spam and viruses. Large networks, like Telus, have mechanisms in
place to block IP addresses almost instantaneously, simply by
updating their routers with a "block list" of addresses.
However, it is common for many different, unrelated Web sites to
share the same IP address."