Detecting and Eliminating Computer Viruses at the Gateway

/Home/Internet Security: E-books

Traditional anti-virus software only stops known computer viruses - stopping undefined computer viruses requires a different approach.

In the past, network administrators scrambled to apply new virus signatures whenever new computer viruses were discovered. While these signatures will stop a known threat, it takes time for anti-virus vendors to develop them. Unfortunately, the newest and most damaging viruses are able to spread so quickly that the damage is done before a signature can be developed and distributed.

In fact, the independent testing laboratory AV-test.org found the response times for major anti-virus software publishers to range from just under 7 hours to almost 30 hours , with the four leading vendors (Sophos, McAfee, Symantec and Trend Micro) clocking in at no less than 12 hours.

In January 2004, the computer virus known as "MyDoom" created mass disruption to corporate resources and reputations as it quickly spread through e-mail networks worldwide. At its peak, MyDoom infected one in every five e-mails transmitted over the Internet. The worm broke records set by previous malware, such as Sobig.F, to become the fastest-spreading virus ever. This incredible propagation speed left many networks vulnerable - despite the presence of anti-virus software - because of the lag time between when the virus outbreak began, and when a virus definition became available.

As a result of recent malware threats, corporations and organizations have learned a painful but important lesson: simply deploying a signature-based solution is no longer enough. Detecting and eliminating computer viruses requires a multi-faceted, rapid-response approach that traditional anti-virus protection cannot provide. Even a single unprotected computer on an enterprise network can bring down the entire system in just minutes, rendering even the most expensive and up-to-date software useless.

Why E-Mail is Particularly Susceptible

In many organizations, e-mail has replaced the telephone as the most useful business tool available. Unfortunately, e-mail has also been a victim of its own success and presents a unique threat to the enterprise network as a whole.

Detecting and eliminating threats has traditionally been the combined responsibility of firewalls, virus scanners, and intrusion detection systems (IDS) set up by enterprises to defend against attacks. Firewalls prevent unauthorized programs from accessing the network, virus scanners scan each PC in the network for malicious code, and gateway servers lock down extraneous ports to protect against unauthorized access.

But key Internet-facing applications, including e-mail are unguarded by firewalls. In order to function, e-mail must expose firewall ports, including port 25, the port used by SMTP (Simple Mail Transfer Protocol) and port 110, the port used by POP (Post Office Protocol).

When a firewall receives a connection on port 25, it generally assumes that the transmission is e-mail and allows it to flow through to the e-mail server. The transmission may very well be a valid e-mail; however, it could also be a virus, spam or something much worse. Firewalls are not able to distinguish between "good" mail and "bad" mail and therefore they are unable ot protect the e-mail application.

Stop E-Mail Threats at the Gateway

Therefore, some sort of protection is needed specifically for e-mail and, since the best place to stop a threat is before it gets inside the network, the protection should be at the e-mail gateway. Protecting the e-mail gateway requires a coordinated effort to combat a host of issues, including spam, viruses, corporate policy infringements, directory harvest attacks, denial of service attacks, phishing, spoofing, and snooping. As e-mail threats evolve, the distinction between each of these types of threats becomes blurred.

Furthermore, accuracy in identifying "bad" e-mails is crucial. Extreme care must be taken to avoid filtering out legitimate e-mails (false positives), which could contain important information from customers or partners.

Historically, enterprises have turned to multiple vendors to solve their e-mail security issues. They have relied on anti-virus vendors to protect them from viruses. They use a separate anti-spam vendor to help cut back on the spam. Then, there are the issues of content filtering, policy enforcement, encryption, and network security. Unfortunatley, attackers are now highly adept at exploiting these non-integrated solutions. This "Swiss cheese" defense has not only been costly, but increasingly ineffective at protecting corporate email systems.

Computer Virus Risks

Recent attacks from various types of computer viruses and worms have had profound effects on computer systems around the world. Enterprises have been brought to their knees and forced to spend billions of dollars cleaning up the mess and rebuilding their infrastructures. While the increased IT costs are clear, there are other risks corporations face with regard to e-mail borne viruses.

System Downtime

E-mail has evolved to be the primary communication tool for most organizations and the loss of e-mail due to attack can severely affect enterprise operations. Beyond the immediate expenses involved in restoring the network, an attack on your enterprise e-mail system can also result in lost hours and days for employees who have come to rely on it to accomplish their daily tasks.

Resource Depletion

The costs of cleaning up after an attack are significant. IT teams are forced to spend considerable time and money repairing virus damage. The damage, however, is rarely contained to network servers. Once inside the network, viruses can quickly infect large numbers of relatively exposed client machines - all of which must be individually cleaned, patched and repaired.

Administration

In the past, when a new vulnerability was discovered, network administrators scrambled to apply security patches from the makers of their anti-virus software and manually reviewed quarantine lists for virus-infected messages. Software manufacturers release patches so frequently that network administrators cannot reasonably be expected to keep up with them all. As stated by Gartner Research, "Enterprises will never be able to patch quickly enough. After all, attackers have nothing else to do." The staggering damage caused by recent computer viruses and malware attacks is clear evidence that manual intervention to institute emergency measures or review quarantined messages is rarely effective against rapidly propagating threats.

Compliance and Liability

Recent Federal regulations such as the Health Insurance Portability and Accountability Act (HIPAA), Gramm-Leach-Bliley Act (GLBA) and Sarbanes-Oxley Act (SoX), require enterprises to protect data residing in mail servers and other internal systems. Security breaches violate these regulations, exposing sensitive data and opening the door to serious sanctions and costly litigation.

Credibility

Falling victim to a virus attack can also result in lost trust from business partners and customers. According to Gartner, "Enterprises that spread viruses, worms, spam and denial-of-service attacks will find not only that malicious software can hinder their profitability, but also that other businesses will disconnect from them if they are considered to be risky." While an attack may not be your fault, it is most certainly your problem.

The Solution

Although signature-based anti-virus systems are inadequate to preventing virus attacks in the first few hours or days of an outbreak, it is possible to identify outbreaks before they infiltrate your organization's network and become a problem. In fact, doing so successfully requires tight integration of several different technologies designed to analyze mail based on many different characteristics. One of the most innovative and important technologies for meeting these threats is known as Anomaly Detection.

Large-scale virus outbreaks create anomalies in mail flow which are identifiable by the message content, source, volume, attachment or any of a number of other indicators. When a particular message appears to be a part of a sudden surge of anomalous messages moving across the internet, the message can be quarantined until virus definitions can be developed to address the new threat.

Anomaly Detection

CipherTrust's IronMail utilizes a unique Anomaly Detection Engine (ADE), which dynamically identifies and responds to abnormal behavior in mail flow. By monitoring "normal" e-mail traffic rates across the Internet, the ADE allows IronMail to identify spikes in traffic that are often the first signal of a malicious attack. Once these spikes are recognized, IronMail units take appropriate action to prevent infiltration of the network.


About the Author

CipherTrust is the leader in anti-spam and email security. Learn more by downloading our free whitepaper, "Next Generation Virus Protection: An Overview of IronMail Zero Day Virus Protection" or by visiting http://www.ciphertrust.com>www.ciphertrust.com.

Written by: CipherTrust