系统软件是指控制和协调计算机及外部设备,支持应用软件开发和运行的系统，是无需用户干预的各种程序的集合，主要功能是调度，监控和维护计算机系统；负责管理计算机系统中各种独立的硬件，使得它们可以协调工作。系统软件使得计算机使用者和其他软件将计算机当作一个整体而不需要顾及到底层每个硬件是如何工作的。
Norton Security Scan 提供对病毒、间谍和其它安全风险程序的扫描和清除。还提供手动扫描和移除病毒、特洛伊木马和入侵工具的功能，这是便携版。
新版本是在线安装版，要从诺顿官网下载和安装，支持中文了。
Norton Security Scan and Clean provides free ondemand scanning and removal or repair of viruses, spyware, and other security risks. This tool is not intended to be a replacement for continuous, realtime protection from the latest security risks.
Norton Security Scan and Clean detects and resolves the following security risks:
Viruses
Programs that infects another program, boot sector, partition sector, or document by inserting itself or attaching itself to that medium. Most viruses just replicate; many also do damage.
Trojan horses
Programs containing malicious code that is disguised as or hiding in someth
ing benign, such as a game or utility.
Hack tools
Tools that are used by a hacker to gain unauthorized access to your computer. One type of hack tool, a keystroke logger, tracks and records your individual keystrokes and can send this information back to the hacker.
Spyware
Programs that can scan systems or monitor activity and relay the information to other computers or locations in cyberspace.
Adware
Programs that facilitate the delivery of advertising content through their own window, or by using another program`s interface.
Trackware
Programs that track system activity, gather system information, or track user habits, and relay this information to thirdparty organizations. The information that is gathered by such programs is neither personally identifiable nor confidential. Trackware programs are installed with the user`s consent, and may also be packaged as part of other software that is installed by the user.
系统软件一般是在计算机系统购买时随机携带的，也可以根据需要另行安装。