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Your precious firewall can't save you now!

Weak or nonexistent implementations in computer security software can leave otherwise-secure computers wide open for attack – so open, in fact, that in some cases it’s as if there’s no firewall running at all.

Speaking at the annual HOPE (Hackers on Planet Earth) conference in New York, security researcher Joe Klein of Command Information said that the internet is full of computers surreptitiously running IPv6, unbeknownst to their owners. Compounding the problem is the number of operating systems shipped with IPv6 enabled by default, which includes Windows Vista, Linux’s 2.6 kernel, Sun’s Solaris, Mac OS X, and a variety of cell phones operating systems, including Windows Mobile 5 and 6.

Computers with a lackluster IPv6 setup – even if they have a strong IPv4 firewall or Intrusion Detection System (IDS) in place – are just as naked in IPv6 space as they would be in IPv4-space without a firewall, with any program that listens for connections allowed to accept them. Most operating systems, by default, use a handful of “listeners” used for networking and internal processes – and it is these listeners that are frequently the first to be targeted in an attack.

A number of computer worms, including Blaster and its follow-up Welchia, worked by exploiting a buffer overflow with Windows’ internal RPC infrastructure, which listens on port 135 and is ordinarily covered up by a firewall.

Network administrators who don’t keep tabs of their systems face a huge risk, said Klein. Operational dangers aside, administrators who work for organizations that have to comply with regulations like HIPAA or Sarbanes-Oxley risk non-compliance if they don’t secure their IPv6 implementations – whether they realize they have one or not.

“Essentially, we have systems that are wide open to a network,” said Klein. “It's like having wireless on your network without knowing it.”

Security researchers have for some time found hackers exploiting IPv6. A 2002 post from Lance Spitzer of the Honeynet project observed a hacker that broke in to a Solaris-based honeypot through normal means, enabled IPv6 connectivity in the OS, and then set up a tunnel out of the network that went into another country. The break-in was only discovered due to network packet-sniffing, and even then Spitzer says he was unable to decode the data being sent out.

One of the biggest threats is the variety of backwards-compatibility schemes designed to tunnel IPv6 traffic through an IPv4 system, like Teredo or the 6to4 system: the very act of tunneling often circumvents firewalls by nature.

“Teredo/ISATAP is currently and will continue to be a major red flag for networks that have both IP versions enabled, because tunneling confuses the heck out of a lot of firewalls and IDS deployments,” said an unnamed DoD security specialist, in an interview with Wired’s Threat Level.

With internet progressives trying to switch the internet to IPv6 as fast as it can – a widget on Command Interface’s web site estimates that the internet will run out of IPv4 addresses in about two and a half years – some fear that technological progress may be outpacing the security that keeps it safe.

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RE: If ya dont need it...
By omnicronx on 7/22/2008 10:38:05 AM , Rating: 2
If you're behind a NAT firewall, this is a very unlikely occurrance.
My guess is that this article is not talking about casual users just behind a firewall, but for say a server running linux or windows 2008 with IPv6 enabled, in which it on the DMZ. As far as the network admin would know, their IPv4 security scheme of which ports to allow would be setup perfectly fine, but leaving IPv6 access open to everyone.

RE: If ya dont need it...
By drebo on 7/22/2008 11:37:44 AM , Rating: 3
Except that if the network is not configured to automatically provision IPv6 (think DHCP), the only IPv6 address that the system is going to have is its link local address, which is not usable by anything not on the same wire (comparable to the IPv4 addresses). An intruder STILL must compromise the system via IPv4 in order to make use of the IPv6 stack to open a back door into the system.

RE: If ya dont need it...
By trejrco on 7/22/2008 12:51:45 PM , Rating: 2
Not always correct; any Win* OS includes several IPv6-in-IPv4 tunneling mechanisms that provide global IPv6 connectivity (bi-directional, that is)


RE: If ya dont need it...
By drebo on 7/22/2008 12:59:18 PM , Rating: 5
That's my point, though. If those tunneling protocols are not set up (and they are not set up by default), then there is no way to gain access to the IPv6 stack of a computer without having already compromised the computer.

The only IPv6 addressing set up by default on a computer is the link local address, which is not accessible except by other devices on the same wire. And by the same wire, I mean the same physical wire, not the same subnet.

RE: If ya dont need it...
By trejrco on 7/23/2008 12:05:01 PM , Rating: 2
(Note - In WinXP, you must enable IPv6 first, in Vista it is already done)

If you get a public (non-NATed) IPv4 address, your machine is running 6to4 ... bidirectional IPv6 access, no user intervention required.

ISATAP is also lit-up by default, looking for an ISATAP router and (if found, or if on public IPv4 address) ... bidirectional IPv6 access, no user intervention required.

And, finally, Teredo. It is lit-up and running by default, possibly needed a manually configured Teredo Server (platform specific) and yielding bidirectional IPv6 access that is able to traverse IPv4 NAT / Stateful Firewalls, (sometimes) no user intervention required.


"I'm an Internet expert too. It's all right to wire the industrial zone only, but there are many problems if other regions of the North are wired." -- North Korean Supreme Commander Kim Jong-il

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