The effectiveness of anti-malware software is the degree to which it can detect, prevent, and remove malicious software (malware) from the system or network. Malware is any software that is designed to harm, exploit, or compromise the functionality, security, or privacy of the system or network1. Some common types of malware are viruses, worms, Trojans, ransomware, spyware, adware, and rootkits2.

One of the best indicators of the effectiveness of anti-malware software is the number of successful attacks by malicious software, which means the number of times that malware has managed to bypass, evade, or disable the anti-malware software and cause damage or disruption to the system or network. The lower the number of successful attacks, the higher the effectiveness of the anti-malware software. This indicator can measure the ability of the anti-malware software to protect the system or network from known and unknown malware threats, and to respond and recover from malware incidents34.

The other options are not the best indicators of the effectiveness of anti-malware software, because:

Number of staff hours lost due to malware attacks is a measure of the impact or consequence of malware attacks on the productivity or performance of the staff. It does not directly reflect the ability of the anti-malware software to detect, prevent, or remove malware, as there may be other factors that affect the staff hours lost, such as the severity of the attack, the availability of backup or recovery systems, or the skills and awareness of the staff5.

Number of downtime hours in business critical servers is a measure of the impact or consequence of malware attacks on the availability or reliability of the servers. It does notdirectly reflect the ability of the anti-malware software to detect, prevent, or remove malware, as there may be other factors that affect the downtime hours, such as the type of the server, the configuration of the network, or the maintenance of the hardware6.

Number of patches made to anti-malware software is a measure of the maintenance or improvement of the anti-malware software. It does not directly reflect the ability of the anti-malware software to detect, prevent, or remove malware, as there may be other factors that affect the number of patches, such as the frequency of the updates, the quality of the software, or the compatibility of the system7.

References =

What is Malware? - Definition from Techopedia

Common Types of Malware and Their Impact - Techopedia

What is Anti-Malware? Everything You Need to Know (2023) - SoftwareLab

The 10 Best Malware Protection Solutions Compared for 2024 - Techopedia

The Cost of Malware Attacks - Security Boulevard

The Impact of Malware on Business - Kaspersky

What is Patch Management? - Definition from Techopedia