Moscow: Computer giant Apple has contracted specialists from Russian anti-virus company Kaspersky Lab to analyse the vulnerabilities of its Mac OS X operating system and improve its security. The OS X security issue became important in early April, when Dr. Web, a Russian computer security company, reported finding botnets -- or networks of compromised computers controlled by hackers -- that included more than 500,000 infected Macs. It was previously thought that Apple computers enjoyed better protection from viruses than computers operating on Microsoft Windows. The appearance of this latest threat has forced Apple to address the security issue, RIA Novosti reported citing the computing.co.uk website. "Apple recently invited us to improve its security. We've begun an analysis of its vulnerabilities, and the malware targeting it," said Kaspersky chief technology officer Nikolai Grebennikov. "Mac OS is really vulnerable," he said. Anti-virus experts, including those at Kaspersky Lab, say the OS X system has a better security record than Windows because the Apple operating system is used on fewer machines. But rising sales of Apple computers, and the appearance of botnets targeting them, indicates that the amount of malware may also increase. Kaspersky Lab is an international group that operates in more than 100 countries worldwide. The company's headquarters are located in Moscow, from which it oversees global operations and business development. According to the company website, Kaspersky Lab is one of the fastest growing IT security companies worldwide. In 2011, Kaspersky Lab's global revenue grew by 14 percent compared to the previous year and exceeded $600 million. Kaspersky Lab currently employs over 2,400 specialists. The company has offices in 29 countries and its products and technologies provide protection for over 300 million users worldwide.