Microsoft on Tuesday released a flood of information on new and previously disclosed holes in a wide range of software products, many of them rated "critical" and well-suited to use by malicious hackers or computer virus writers, according to one security expert.

The company published four security bulletins, MS04-011, 012, 013 and 014 containing patches for 20 unique software vulnerabilities. Critical holes were found in the Internet Explorer Web browser, a standard Windows component for managing local system security and authentication, the Microsoft Secure Sockets Layer library (SSL) and Remote Procedure Call (RPC) Runtime Library, which is installed with Windows, Microsoft said.

The software patches touched a wide range of Microsoft's products, from Windows 98 through Windows Server 2003 64-bit edition, as well as a number of versions of the Outlook Express e-mail program.

Among the most critical holes Microsoft warned customers about are:

• A buffer overrun vulnerability in the Local Security Authority Subsystem Service (LSASS), which is used to authenticate users locally and also in client-server environments. LSASS also has features used by Active Directory utilities. An attacker who could exploit the LSASS vulnerability could remotely attack and take total control of Windows 2000 and Windows XP systems. The same vulnerability does not affect Windows 98 or NT, and is rated "low" for Windows Server 2003, meaning that it is extremely difficult to exploit or will have only minimal impact on the system if exploited, according to Microsoft.
• A buffer overrun in the Private Communications Transport (PCT) protocol, which is part of Microsoft's SSL library, which is used to secure communications between servers and clients on public networks and the Internet. PCT is a protocol in that library that was developed by Microsoft and Visa International to conduct encrypted communication on the Internet, Microsoft said.

An attacker who could exploit the PCT hole could take complete control of affected systems, installing programs, viewing, modifying or deleting data or changing user access to the system. Attackers could exploit the flaw by sending a TCP message to a vulnerable system using SSL. The message would have to be designed to cause the buffer overrun and run the attacker's code on the machine, the company said.

The IDG News Service is a Network World affiliate.