Update (6/18): Microsoft confirmed today that they plan to release a public beta of Microsoft Security Essentials (formerly codenamed Morro) this Tuesday June 23.
Following up from a report on Neowin yesterday, Ars Technica has revealed that Microsoft's upcoming anti-virus software has dropped the Morro moniker and is now officially known as Microsoft Security Essentials. They have uploaded a new set of screenshots briefly going over the installation process, some of the program's features, and showing the updated user interface.
Based on the recently leaked build, Ars reports that MSE has separate installers for Windows XP, Windows Vista, and Windows 7 in both 32 and 64-bit flavors. File sizes are also rather small, ranging from 3 MB to 7 MB. The security software will completely replace Windows' built-in Defender, and should offer real-time protection against viruses, spyware, rootkits, and Trojans. Although Microsoft Security Essentials is already being tested internally, the company is expected to offer a public beta "soon," and have the final version ready later this year.