The warning comes after the disclosure this week of two critical flaws in Skype's software, one of which could allow malicious hackers to take complete control of compromised systems.

One of the flaws is a buffer overflow error in Skype's user client for Windows that could allow attackers to execute arbitrary code on compromised systems, according to a statement from the company. The other vulnerability is a heap overflow flaw in a networking routine affecting Skype clients for all platforms. That flaw could crash the client software.

Fixes for both problems have been released.

Skype, which was recently acquired by eBay Inc. for US$2.6 billion, offers downloadable software that allows PC users to make free Internet telephone calls to each other and low-cost calls to telephone users.

So far, Skype has garnered more than 61 million registered users, approximately 30 percent of whom use it for business purposes, according to the company. Almost all of that adoption has been in Europe and Asia, though analysts expect Skype to eventually gain wide accepted in the U.S. as well.