Virgin Media customers found themselves blocked from accessing the FileServe file-hosting site last week as a result of the Internet Watch Foundation blacklisting a single FileServe URL.
The problem has now been cleared up, although not before
inconveniencing people who use the cyberlocker service for legitimate
business purposes. The Open Rights Group has described the issue as
demonstrating inherent flaws in site-blocking schemes.
"Customers may have experienced problems accessing FileServe as a
result of a specific URL being on the IWF [Internet Watch Foundation]
watchlist," a Virgin Media spokesperson told ZDNet UK on Monday.
"We've spoken to the IWF and FileServe to resolve the issue, and our
customers should now have full access again."
The issue first became apparent on Wednesday, when Virgin Media
customer 'SandyB' complained
on the ISP's forum of not being able to access FileServe.
"I know the majority don't use these one-click file-hosting sites
legitimately, but I do, and it's currently interfering with my work,"
In the ensuing conversation, it emerged that other Virgin Media
customers also could not access FileServe. When they tried to do so,
they were met with a splash screen telling them: "The IWF has recently
implemented changes that may affect your download ability on the
Virgin Media's systems respond to a specific URL's inclusion on the
IWF blacklist by sending all customers' traffic to the relevant host
through a web proxy that filters out the bad URL, supposedly while
leaving the rest of the traffic alone.
However, in this case FileServe's systems interpreted the vast
amount of traffic coming from the proxy's limited set of IP addresses
as a potential malicious attack. In response, FileServe blocked all
traffic coming from Virgin Media's customers.
This shows that blocking technologies, when they are targeted at any type of service with a large number of users, are very prone to failure.– Jim Killock, Open Rights Group
"We've contacted the IWF, and they're confirmed [sic] that FileServe.com
is not on their watchlist, but that a specific URL on FileServe is,"
Wilkin wrote. "They've temporarily removed that URL from the watchlist
and are currently attempting to contact FileServe about the claims
they've made... to try and resolve this. The updated watchlist was
published at 6pm today so it should already be having an effect."
Wilkin added that Virgin Media has dealt with similar "previous
problems with file-sharing services" by getting the companies behind
such services to whitelist the ISP's proxy IP addresses.
The IWF told ZDNet UK on Monday that it was not responsible for the
way ISPs implement its blacklist, which it said was intended as "a
short-term disruption tactic which can help protect internet users
from stumbling across [child sexual abuse] images, whilst processes to
have them removed are instigated".
"IWF's role in this blocking initiative is restricted to the
compilation and provision of a list: the blocking solution is entirely
a matter for the company deploying the list," the non-profit
organisation said. "Our list is designed and provided for blocking
specific URLs only. Any decision to convert or adapt the list to block
whole domains may lead to the overblocking of legitimate content and
is not supported by the IWF."
According to Jim Killock, head of online rights activists the Open
Rights Group, the accidental blocking of legitimate content has become
"quite a common occurrence".
"This shows that blocking technologies, when they are targeted at
any type of service with a large number of users, are very prone to
failure," Killock told ZDNet UK. "They are hard to scale properly, and
the costs of scaling them are likely to be enormous."
Killock added that blocking should be "an absolute last resort and
not some sort of substitute for removing illegal material", and also
criticised FileServe's splash screen for not being completely
transparent about the reason for the service blockage.