Cisco PIX 525 Especificações descarregar pdf (Página 36)

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Cisco PIX Firewall and VPN Configuration Guide

78-15033-01

Chapter 1 Getting Started

Protecting Your Network from Attack

ActiveX Blocking

ActiveX controls, formerly known as OLE or OCX controls, are components that can be inserted into a

web page or other application. The PIX

Firewall ActiveX blocking feature blocks HTML <object>

commands and comments them out of the HTML web page. As a technology, ActiveX creates many

potential problems for the network clients including causing workstations to fail, introducing network

security problems, being used to attack servers, or being used to host attacks against servers.

Java Filtering

The Java Filtering feature lets you prevent Java applets from being downloaded by a system on a

protected network. Java applets are executable programs that may be prohibited by some security

policies because they can enable certain methods of attacking a protected network.

URL Filtering

You can use access control lists to prevent outbound access to specific websites, but configuring and

managing web usage this way is not very practical because of the size and dynamic nature of the Internet.

The recommended solution is to use the PIX

Firewall in conjunction with a separate server running one

of the following Internet filtering products:

• Websense Enterprise web filtering application (supported by PIX Firewall Version 5.3 or higher)

• Filtering by N2H2 for IFP-enabled devices (supported by PIX Firewall Version 6.2 or higher)

Compared to using access control lists, this reduces the administrative task and improves filtering

effectiveness. Also, because URL filtering is handled on a separate platform, the performance of the

PIX

Firewall is much less affected.

The PIX Firewall checks outgoing URL requests with the policy defined on the URL filtering server.

PIX

Firewall either permits or denies the connection, based on the response from the filtering server.

For further information, refer to either of the following websites:

http://www.websense.com

http://www.n2h2.com

Note PIX Firewall Version 6.3 or higher supports filtering of HTTPS and FTP sites when using the Websense

filtering server. PIX

Firewall Version 6.2 or higher supports filtering of long URLs, such as those

generated by search engines.

Configurable Proxy Pinging

The Configurable Proxy Pinging feature lets you control ICMP access to PIX Firewall interfaces. This

feature shields PIX

Firewall interfaces from detection by users on an external network.

Note We recommend that you grant permission for ICMP unreachable message type 3. Denying ICMP

unreachable messages disables ICMP Path MTU discovery, which can halt IPSec and PPTP traffic.

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