It is well known that Anti-Virus technology is fallible and will continue to be so by design. The landscape (Threatscape?) is always changing and AV systems will typically update their malware signature repositories at least once per day in an attempt to keep up with the new threats that have been isolated since the previous update.

So how secure does your organization need to be? 80%? 90%? Because if you rely on traditional anti-virus defenses this is the best you can hope to achieve unless you implement additional defense layers such as FIM (file integrity monitoring) and SIEM (event log analysis).

Anti-Virus Technology – Complete With Malware Blind spots

Any Anti Virus software has an inherent weakness in that it relies on a library of malware ‘signatures’ to identify the viruses, Trojans and worms it is seeking to remove.

This repository of malware signatures is regularly updated, sometimes several times a day depending on the developer of the software being used. The problem is that the AV developer usually needs to have direct experience of any new strains of malware in order to counteract them. The concept of a 'zero day' threat is one that uses a new variant of malware yet to be identified by the AV system.

By definition, AV systems are blind to ‘zero day’ threats, even to the point whereby new versions of an existing malware strain may be able to evade detection. Modern malware often incorporates the means to mutate, allowing it to change its makeup every time it is propagated and so improve its effectiveness at evading the AV system.

Similarly other automated security technologies, such as the sandbox or quarantine approach, that aim to block or remove malware all suffer from the same blind spots. If the malware is new though – a zero day threat – then by definition there is no signature because it has not been identified before. The unfortunate reality is that the unseen cyber-enemy also knows that new is best if they want their malware to evade detection. This is evident by the fact that in excess of 10 million new malware samples will be identified in any 6 month period.

In other words most organizations typically have very effective defenses against known enemies – any malware that has been previously identified will be stopped dead in its tracks by the IPS, anti-virus system, or any other web/mail filtering with sandbox technology. However, it is also true that the majority of these same organizations have little or no protection against the zero day threat.

File Integrity Monitoring – The 2nd Line Anti-Virus Defense System for When Your Anti-Virus System Fails

File Integrity Monitoring serves to record any changes to the file system i.e. core operating system files or program components. In this way, any malware entering your key server platforms will be detected, no matter how subtle or stealthy the attack.

In addition FIM Technology will also ensure other vulnerabilities are screened out from your systems by ensuring best practices in securely configuring your Operating Systems have been applied.

For example, any configuration settings such as user accounts, password policy, running services and processes, installed software, management and monitoring functions are all potential vectors for security breaches. In the Windows environment, the Windows Local Security Policy has been gradually extended over time to include greater restrictions to numerous functions that have been exploited in the past but this in itself is a highly complex area to configure correctly. To then maintain systems in this secure configured state is impossible without automated file integrity monitoring technology.

Likewise SIEM or Security Information and Event Management systems are designed to gather and analyze all system audit trails/event logs and correlate these with other security information to present a true picture of whether anything unusual and potentially security threatening is happening.

It is telling that widely adopted and practiced security standards such as the PCI DSS place these elements at their core as a means of maintaining system security and verifying that key processes like Change Management are being observed.


Anti-virus technology is an essential and highly valuable line of defense for any organization. However, it is vital that the limitations and therefore vulnerabilities of this technology are understood and additional layers of security implemented to compensate. File Integrity Monitoring and Event Log Analysis are the ideal counterparts to an Anti-Virus system in order to provide complete security against the modern malware threat.

Author: Mark Kedgley

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