Case Study

Rapid Red Services, Inc., was quite happy with its newfound savings ever since they switched all long distance to Teletrinity, the regional VoIP provider. The business case for VoIP turned out to be an easy sell. However, when the latest bill ended up on Glen Smith's desk, he knew something wasn't right.

As CIO, Smith knew such problems could run deep. He had been in the business long enough to know there were no such things as ghosts in the machine. And there was just no way the company's VoIP usage increased by 1000 percent in just one month. Hackers had to be involved.

While his team dealt with the technical problem, Smith dealt directly with the billing problem. However, as Smith originally suspected, Teletrinity denied any wrongdoing and refused to issue a refund. The company claimed the calls were authenticated legitimately on Rapid Red's trunk line and seemed to come out of its office. So to get to the root of the problem, Smith had to go back to his security team.

The Rapid Red security team consisted of security specialists from various backgrounds, but none in VoIP, so they called in an expert. The expert needed little time to understand the issue and discover the source of the problem. He explained that Teletrinity acts as the local partner and wholesale reseller of VoIP "minutes" and card services for several tier 1 VoIP peering providers. The Teletrinity infrastructure uses equipment from the major VoIP vendors, some of whom lock their clients into a proprietary environment they control so they can log in remotely to their clients' systems as root, although the clients could only access the system through an unprivileged interface. He also explained that he had heard rumors of staff from these vendors' Eastern European offices abusing their knowledge of remote access procedures to compromise a customer's infrastructure. Such rumors had been, of course, denied by the vendors, yet they hadn't provided an alternative explanation for some of the strange billing issues occurring in their systems.

After a few days of tests and verification on the VoIP infrastructure that they leased from Teletrinity, the VoIP expert concluded that the security was based on the worst of the "obscurity" doctrine. The VoIP equipment vendor's idea of security was to remove execute permissions on tools such as w and who and to change the root password every few hours with a known sequence that only they could know about. Furthermore, after seeking out VoIP hackers on IRC and SILC, the VoIP expert noted the fact that software deployed by Teletrinity is routinely cracked by pirates who resell it at a fraction of its outrageously high selling price.

At this point, Smith knew that Teletrinity would not be of any help since the company could not help themselves, and he procured the expert to perform deeper forensic investigations into the equipment. Cracking open the infrastructure did violate the terms of the contract, but this was also something he knew the Teletrinity engineers would only try to cover up if they could. He needed the smoking gun to better protest the costs.

The expert soon discovered that an unauthorized intruder had obtained privileged access to the main Teletrinity gateway processing Rapid Red calls. The intruder knew VoIP equipment internals and was able to remove her tracks by deleting relevant Call

Detail Records from the platform and removing traces of her actions in the logs. He could not tell the origin of the attack vector used to compromise the system without hacking the the gateway himself. However, he could identify the initial attack vector. The web server logs showed intensive brute-force attempts to discover valid usernames of corporate clients. The PIN code protecting the client accounts had also been brute-forced, and in both cases the company had used obvious combinations of the two that could be easily discovered by brute-forcing tools. Yet the latest incident showed that someone was able to access the VoIP equipment with the highest privileges and compromise the platform with ease. This was no random hacking.

Once the platform was compromised, the intruder was able to route traffic through it. At the time this traffic was routed using Rapid Red's trunk line, resulting in a massive increase in billable records. The tactic of such VoIP hackers is to max out the hacked platform capacity by offering cheap routes on the global VoIP wholesale market. This market is very dynamic with hundreds of players coming and going. It escapes any regulatory authority and as such is not accountable to any standards or government regulator. The players of those markets will, in turn, resell the routes they negotiate on the marketplace to smaller players who, in turn, resell the minutes to Internet cafes and VoIP service providers that, in turn, sell the VoIP services and minutes to the final users, residential or corporate. In any case, it is a maze of short-term deals, shady contracts, and alternative payment systems—simply put, a law enforcement nightmare, as the number of legal jurisdictions in such crimes overlap national boundaries and make it virtually impossible to identify and prosecute perpetrators successfully.

Smith knew that chasing down any possible leads the expert proposed made no sense. Even if he could determine who the attacker was, she would be out of reach of any law enforcement officers even if he could find those IT-savvy enough to take the case.

Smith compiled the papers he needed to get Teletrinity to correct the billing error and put them in a large envelope. He knew that even if Teletrinity reduced the billing charges, it had cost him an equal amount in hours to contest it, which meant he could not afford to be dependent upon another prepackaged solution again. He called his team together and proposed they build their own VoIP infrastructure immediately from open sources with a strong focus on security.

oice over IP (VoIP) refers to the transmission of speech over the Internet or through any other IP data network. Its architecture is very different than traditional circuit-

switched telephony, even though it serves the same purpose. In classic telephony, each conversation has a private physical circuit and a dedicated infrastructure that solely governs its transmission. In VoIP environments, voice and signaling are multiplexed and travel as normal data inside regular packet-switched IP networks.

The VoIP solution is conceptually superior to traditional Public Switched Telephone Network (PSTN) phone lines in many ways. It provides a cheaper and clearer alternative, and because of that, it will most likely capture a significant portion of the telephony market. Indeed, the VoIP feature that has attracted the most attention is its cost-saving potential. By moving away from the public-switched telephone networks, long-distance phone calls become very inexpensive. VoIP is also cost effective because all of an organization's electronic traffic (phone and data) can be converged into one physical network, bypassing the need for separate Private Branch eXchange (PBX) lines. Although the initial startup cost is significant, substantial savings can definitely result from managing only one network and eliminating the need to sustain a legacy telephony system in an increasingly Internet-centered world.

The flexibility of VoIP systems is attractive, but the integration of security measures into this still-evolving technology is very complex. VoIP conversations, encoded with an appropriate Compression/Decompression (CoDec) algorithm and streamed over traditional networks, behave as normal IP data, but at the same time they must obey the rules imposed by classic telephony in terms of quality of service and availability. Developing a robust architecture that respects these constraints is not an easy task, and the fact that VoIP is still a relatively young technology makes it even more difficult. Although a true standard will probably emerge in the near future, as of today you can choose from many different architectures and protocols. Since a widely used open standard has yet to be developed, VoIP solutions are likely to include a number of proprietary elements, which adds uncertainty to the strength of this new technology and can limit an organization's future choices.

This chapter introduces the challenges of auditing and securing converging voice and data networks for Linux users and outlines steps needed to help secure an organization's VoIP infrastructure.

VoIP is subject to security issues inherited from both data networks and telephony. Classic telephony security attacks involving signaling protocol manipulations have their counterparts in VoIP, and the main purpose of the attackers remains the same—fraud. On the other hand, data networks' security issues are far more complex and offer larger avenues of attack than traditional phreaking. From physical to application layer, all network security items are relevant to VoIP security. In terms of exposure, the transport of voice data over the Internet multiplies the attack surface and will surely lead to more attacks against this technology. Furthermore, the synergies of the two conflicting aspects

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