Malicious code masquerading as a trusted application could trick a ZoneAlarm firewall into letting it connect to the Internet, security experts have warned.
The issue affects the popular free ZoneAlarm firewall and default installations of version 5.5 and earlier of the paid product, maker Zone Labs said in a security advisory on Thursday. Default installations of the Check Point Integrity Client are also affected, but the paid ZoneAlarm 6.0 products, released in July, are not, Zone Labs said.
"If successfully exploited, a malicious program may be able to access the network via a trusted program," Zone Labs, which is part of Check Point, said in its advisory. If the malicious program attempted a direct connection to the Internet, it would be blocked by the firewall.
An example of the technique was published earlier this week by security researcher Debasis Mohanty. The method uses a Windows mechanism for linking applications, according to Mohanty, who also said the problem may exist in other firewall products.
An attacker could trick the firewall by linking a keystroke logger or other malicious program to another application — Internet Explorer, for example. When the keystroke logger subsequently sends its captured data out, the firewall would see IE, not the spyware, accessing the Internet and allow the connection.
However, Zone Labs has not seen any malicious software that actually uses this trick, said John LaCour, director of security services at the software maker. "It is a theoretical attack that we don't see used in the real world," he said. Zone Labs rates the issue "low risk".
Zone Labs has no current plans to update its free firewall product to protect against this issue, the company said. Its paid products offer protection against the problem because of additional technology, called an operating system firewall, that is not part of the free network firewall, LaCour said.
"The network firewall is doing its job. This issue involves how different applications on a system interact, and that is not a function of a network firewall; it is a function of an OS firewall," LaCour said. "If a user wants to have a higher level of protection, then we have a product available to do that."
Users of the paid ZoneAlarm 5.5 products and Check Point Integrity Client versions 6.0 and 5.5 can protect themselves by enabling the "Advanced Program Control" feature, Zone Labs said.
Talkback
The intrusion detection/antispyware program All-Seeing Eye from Fortego Security (http://www.fortego.com/ase) will immediately detect when unknown code is loaded into other processes (e.g. Internet Explorer) to do evil things like this.
I've found it an extremely useful complement to my firewall and normal antivirus software, and it's completely free. I can really recommend everyone to take a look at it.
as zonealarm says its not going to bother fixing this flaw for the free firewall it provides i think ill go find another free firewall provider! how incredibly stupid of them to say theyre not going to fix a flaw, just goes to show how little they care for the millions of people who use their products,eveyone in the software business knows its beter to give away your software than have consumers use a rivals products as you can keep pestering people to upgrade even if they dont,if zonalarm dont say theyll fix this flaw within next week by telling zdnet im leaving this company for good theyre atitude to securing customers data is outragous.