tailieunhanh - e mail virus protection handbook phần 6

Tôi đã cài đặt McAfee VirusScan 5 và Norton AntiVirus 2000 khi tôi cài đặt Trend Micro PC-cillin 2000. Nó đã phá vỡ quá trình cài đặt với thông điệp rằng họ đã phát hiện khác chống virus (AV) ứng dụng. Chạy nhiều ứng dụng | 232 Chapter 7 Personal Firewalls An ACL in the file sense is a mechanism for enforcing a particular set of permissions for a file or directory. This could be either on a per-user or per-process basis. For example if someone is logged into your computers as guest you might not want them to have access to your documents. You would have an ACL that said something like guest no access. For a process example consider your Web browser. You might want to have a rule as a backup protection mechanism that says your browser can t write to most of your hard drive. That way if some attacker takes advantage of a hole in your browser software your backup mechanism might save you. There is an example of this type of ACL in the eSafe section later in this chapter. A network ACL is used to define which addresses and ports are allowed or blocked. An ACL entry typically includes some portion of the following an address or range or 24 a list or range of ports 80 25 1023 and a protocol type Transmission Control Protocol or TCP User Datagram Protocol or UDP or Internet Control Message Protocol or ICMP . Other things that may be included in an ACL include time information enforced during certain hours or temporary entries that may be added in response to other traffic that has gone by. Since the term ACL is pretty generic it gets fairly vendor -specific beyond those simple terms. Some firewall vendors call it a rule set. Some firewalls can have much more complicated things besides just allowing or not allowing certain ports or files. While discussing specific products in this chapter there will be a number of examples of ACLs. Execution Control List ECL An Execution Control List ECL is similar in spirit to an ACL but it controls which programs may be executed. This may seem to be a bit redundant if an ACL is in place. For example most file ACL software will allow you to mark files with an execute no execute flag. But ECLs are not redundant. The reason is that not .