Archive for the ‘Exploits’ Category

Serious DNS Vulnerability

July 15, 2008

Older versions of almost every popular implementation of DNS (eg. BIND, Windows, Cisco, Solaris, Juniper) have a vulnerability which would allow an attacker to “cache-poison” the server. This means that a compromised server, possibly your ISP’s, could direct you to fraudulent websites.

For example, this sort of attack could mean that if you typed into your browser, a cache-poisoned DNS could direct you to an IP address that is not operated by PayPal, but the address bar would still say This attack can not spoof the PayPal SSL certificates, but could list one with a similar name, making this an extremely dangerous phishing technique.

One would hope all the major ISPs and public name servers would have patched this vulnerability, but it’s likely that smaller servers, such as at businesses, universities or individuals, may not have.

Test your DNS server here, many large ISPs have been very slow to patch:

If this test shows your DNS to be vulnarable, change your DNS settings to the ones specified at OpenDNS.

Vulnerability specifications:

gpcode.ak: New-gen Ransomware

June 10, 2008

This isn’t new, but worrying. A ransomware virus from over a year ago, called ‘gpcode’ has resurfaced. The new version is called ‘gpcode.ak’.

What’s interesting about this virus is that, when infection occurs, it encrypts a victim’s documents (.doc, .pdf, etc) and leaves a ransom note on the computer demanding money in return for the decryption key. The original version of this particular virus used a 660-bit asymmetric key which was eventually cracked, but this new version uses 1024-bits. The internet security company Kaspersky has stated:

“Along with antivirus companies around the world, we’re faced with the task of cracking the RSA 1024-bit key. This is a huge cryptographic challenge. We estimate it would take around 15 million modern computers, running for about a year, to crack such a key.”

Obviously this is very bad news for anyone infected by gpcode.ak, but it does provide some evidence as to the strength of good cryptography. For example, in the OpenVPN guide I’m putting together, I recommend using a 2048-bit key for certificate generation. That’s 2^1024 harder to crack than a 1024-bit key and, going on Kaspersky’s calculation, it would take 15 million modern computers 2^1024 years to crack. While computers are always becoming more powerful, this sort of key strength will surely remain safe for some time to come.

There’s a good page explaining all the details of gpcode.ak here.

SilentBanker: Stealing Money While You Wait

April 7, 2008

Online banking is a precarious thing. While it’s great to avoid the line at the bank, the security risks that come with this convenience are immense. Online banking has broken down the geographic and physical limitations that previously prevented fraudsters from thinking global.

To get to the point, there are some really powerful, cleverly designed trojans in the wild, designed to steal hard earned cash from under our noses.

One that’s had a lot of attention over the last couple of months is SilentBanker. While other banking trojans indiscriminately log keystrokes, take screenshots and/or redirect you to phishing sites, SilentBanker takes a much more tactful and targeted approach.

SilentBanker’s evil genius lies in its ability to dynamically adapt attacks based on which banking site you use. The administrators of this trojan continually create profiles for new banks and, once a bank is profiled, SilentBanker can then perform a host of tricks to swipe cash from unsuspecting users. The most worrying are HTML code injection to prompt users for extra credentials, and the ability to dynamically modify the destination account numbers during live transactions, sending funds to a hacker’s account, rather than the intended recipient. In the case of the latter, the user is not presented with any evidence of the fraudulent transaction. Confirmation pages are presented with the original, user submitted details.

While other attacks will often spike a user’s attention when thousands of dollars go missing from an account, trojans like SilentBanker are much less likely to draw such attention, because they only withdraw amount which users specify. There is nothing unexpected, unless the intended recipient of a transactions start asking their whereabouts of payments.

The best ways to protect against trojans like this are up-to-date antivirus, a firewall with application control and being alert to any change in the authentication process for your online account.

Symantec has rated SilentBanker as a low risk threat, largely due to it’s limited distribution, so it’s a case of be alert, not alarmed. However, more will follow.

Symantec have done a good technical write up:

And Sophos have a write up on a similar trojan called Zbot:

Hack a Mac: PWN2OWN at CanSecWest

April 1, 2008

A security researcher at a Canadian security conference won over $10,000 in prize money for attacking a completely patched OSX system.

Hackers in the “PWN2OWN” competition at CanSecWest were given the choice of attacking Vista SP1, OSX 10.5.2 or Ubunti 7.10. The winner of the competition, Charlie Miller, chose OSX as his platform, explaining “it was the easiest one of the three”. He exploited a Safari vulnerability and compromised the system within the space of two minutes.

This doesn’t mean that there will suddenly be an deluge of OSX attacks. Windows is, without doubt, the platform of choice to exploit. Just a heads up for all those Mac users out there.

Some RFID Cards Cracked

March 11, 2008

I don’t understand why people develop proprietary encryption. Seems like a lot of effort for no gain. AES is rock solid and there are a number of secure hashing standards… and they’re free to use.

Here’s the reason this issue has come up. NXP Semiconductors, an RFID access card manufacturer, have sold over a billion of their ‘Mifare Classic’ RFID cards. Recently, some University of Virginia researchers physically opened one of these cards and, using a microscope to analyse the physical logic gates, worked out the proprietary algorithm. It’s called ‘Crypto1’.

Turns out Crypto1 is a dud. It produces cryptographically weak output allowing an attacker to guess the key in a matter of minutes. Because its RFID, an attacker doesn’t even need physical access to the card. Seeing as these cards are potentially used as access tokens for buildings around the world, this could potentially be a threat to your company’s security. We may never know how big this issue becomes, seeing as it would be unwise to publicly announce that you use a broken security technology.

The point here is that companies shouldn’t use proprietary security. They should use opens standards like AES, which has been pounded on, without fault, for years. Security through obscurity is a poor practice.

To the credit of NXP, they have now released the ‘Mifare Plus‘, which is backwards-compatible with the ‘Classic’ system, and supports AES. It ain’t a free upgrade though.

Browser Vulnerabilities

March 8, 2008

I just checked some browser security stats on Secunia. Not surprisingly, Internet Explorer 7 holds the crown for the most unpatched vulnerabilities at the moment. At the time of writing, it has 7 unpatched out of the 22 which have been made public since its release. Firefox 2 comes in number second, with 4 unpatched out of 21 public vulnerabilities.

My favourite browser, Opera 9, has zero unpatched flaws, and has only had 14 known flaws since release.




More details here: IE7 , Firefox 2, Opera 9

Frozen Memory Hack

March 5, 2008

A bunch of Princeton researchers figured out that your RAM actually keeps data, once the power’s cut, for a lot longer than commonly thought. They also worked out that if you flip a compressed air can and spray it on the RAM chip, it will retain data for an even longer period of time. They then developed a tool that can boot from a USB device and steal encryption keys (which are stored in RAM) for whole disk encryption tools like TrueCrypt, Windows BitLocker and Mac FileVault.

Should we be concerned? Not really.

For one, a hacker needs physical access to your computer, and, unless you’ve got something super valuable on your computer (that someone else knows about), noone is going to bother going to all the effort. In any case, if your computer was on, surely they’d just access the data on the spot… or steal the whole thing. The other thing is, after about a minute, the data is as good as gone from your RAM, so if anyone’s concerned about it, the problem can be solved by just hanging around for a minute or two after you switch your machine off. Furthermore, this only really affects whole disk or system partition encryption. If you store your really important files in a encrypted volume file (with TrueCrypt), the encryption key will be securely erased when you unmount. Hence, this attack wouldn’t work.

The only everyday situation where I could see this being a problem is if you have particularly untrustworthy co-workers. They could perform this hack while you take a toilet break and then, with knowledge of the key, access your computer at a later date. They could also use Winlockpwn to bypass your Windows password.

To sum up, it’s annoying that this is possible, but it won’t really affect most people. Congrats to the Princeton guys though. This is some very clever engineering.