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> Chapter 9 - Firewall > Security policies > Security profiles

Security profiles

Where security policies provide the instructions to the FortiGate unit for controlling what traffic is allowed through the device, the Security profiles provide the screening that filters the content coming and going on the network. Security profiles enable you to instruct the FortiGate unit about what to look for in the traffic that you don’t want, or want to monitor, as it passes through the device.

A security profile is a group of options and filters that you can apply to one or more firewall policies. Security profiles can be used by more than one security policy. You can configure sets of security profiles for the traffic types handled by a set of security policies that require identical protection levels and types, rather than repeatedly configuring those same security profile settings for each individual security policy.

For example, while traffic between trusted and untrusted networks might need strict antivirus protection, traffic between trusted internal addresses might need moderate antivirus protection. To provide the different levels of protection, you might configure two separate profiles: one for traffic between trusted networks, and one for traffic between trusted and untrusted networks.

Security profiles are available for various unwanted traffic and network threats. Each are configured separately and can be used in different groupings as needed. You configure security profiles in the Security Profiles menu and applied when creating a security policy by selecting the security profile type.

There is a separate handbook for the topic of the Security Profiles, but because the Security Profiles are applied through the Firewall policies it makes sense to have at least a basic idea of what the security profile do and how they integrate into the FortiGate's firewall policies. The following is a listing and a brief description of what the security profiles offer by way of functionality and how they can be configured into the firewall policies.


Antivirus is used as a catch all term to describe the technology for protection against the transmission of malicious computer code sometimes referred to as malware. As anyone who has listened to the media has heard that the Internet can be a dangerous place filled with malware of various flavours. Currently, the malware that is most common in the Internet, in descending order, is Trojan horses, viruses, worms, adware, back door exploits, spyware and other variations. In recent years, not only has the volume of malicious software become greater than would have been believed when it first appeared but the level of sophistication has risen as well.

The Antivirus Filter works by inspecting the traffic that is about to be transmitted through the FortiGate. To increase the efficiency of effort it only inspects the traffic being transmitted via the protocols that it has been configured to check. Before the data moves across the FortiGate firewall from one interface to another it is checked for attributes or signatures that have been known to be associated with malware. If malware is detected, it is removed.

Web filtering

Malicious code is not the only thing to be wary of on the Internet. There is also the actual content. While the content will not damage or steal information from your computer there is still a number of reasons that would require protection from it.

In a setting where there are children or other sensitive people using the access provided by a connected computer there is a need to make sure that images or information that is not appropriate is not inadvertently displayed to them. Even if there is supervision, in the time it takes to recognize something that is inappropriate and then properly react can expose those we wish to protect. It is more efficient to make sure that the content cannot reach the screen in the first place.

In an organizational setting, there is still the expectation that organization will do what it can to prevent inappropriate content from getting onto the computer screens and thus provoking an Human Resources incident. There is also the potential loss of productivity that can take place if people have unfiltered access to the Internet. Some organizations prefer to limit the amount of distractions available to tempt their workers away from their duties.

The Web filter works primarily by looking at the destination location request for a HTTP(S) request made by the sending computer. If the URL is on a list that you have configured to list unwanted sites, the connection will be disallowed. If the site is part of a category of sites that you have configured to deny connections to the session will also be denied. You can also configure the content filter to check for specific key strings of data on the actual web site and if any of those strings of data appear the connection will not be allowed.

Application control

Application control is designed to allow you to determine what applications are operating on your network and to the also filter the use of these applications as required. Application control is also for outgoing traffic to prevent the use of applications that are against an organization’s policy from crossing the network gateway to other networks. An example of this would be the use of proxy servers to circumvent the restrictions put in place using the Web Filtering.

Intrusion protection (IPS)

Intrusion Prevention System is almost self explanatory. In the same way that there is malware out on the Internet that the network needs to be protected from there are also people out there that take a more targeted approach to malicious cyber activity. No operating system is perfect and new vulnerabilities are being discovered all of the time. An intrusion prevention system is designed to look for activity or behavior that is consistent with attacks against your network. When attack like behavior is detected it can either be dropped or just monitored depending on the approach that you would like to take.

As new vulnerabilities are discovered they can be added to the IPS database so that the protection is current.

Email filtering

Spam or unsolicited bulk email is said to account for approximately 90% of the email traffic on the Internet. Sorting through it is both time consuming and frustrating. By putting an email filter on policies that handle email traffic, the amount of spam that users have to deal with can be greatly reduced.

Data Leak Prevention (DLP)

Data Leak Prevention is used to prevent sensitive information from leaving your network. When people think of security in the cyber-world one of the most common images is that of a hacker penetrating your network and making off with your sensitive information, but the other way that you can lose sensitive data is if someone already on the inside of your network sends it out. This does not have to be an act of industrial espionage. It can just be a case of not knowing the policies of the organization or a lack of knowledge of security or laws concerning privacy.

For instance, a company may have a policy that they will not reveal anyone’s Social Security number, but an employee emails a number of documents to another company that included a lengthy document that has a Social Security number buried deep within it. There is not malicious intent but if the information got out there could be repercussions.

If an organization has any information in a digital format that it cannot afford for financial or legal reasons, to leave its network, it makes sense to have Data Leak Prevention in place as an additional layer of protection.


Voice over IP is essentially the protocols for transmitting voice or other multimedia communications over Internet Protocol networks such as the Internet. The Security Profiles VoIP options apply the SIP Application Level Gateway (ALG) to support SIP through the FortiGate unit. The SIP ALG can also be used to protect networks from SIP-based attacks.


Internet Content Adaptation Protocol (ICAP) off loads HTTP traffic to another location for specialized processing. The purpose of this module when triggered is to send the incoming HTTP traffic over to a remote server to be processed thus taking some of the strain off of the resources of the FortiGate unit. The reasons for the specialized process could be anything from more sophisticated Antivirus to manipulation of the HTTP headers and URLs.

EndPoint control

EndPoint Control makes sure that certain standards are kept. When a computer on the Internet becomes connected to the FortiGate unit by VPN that computer is now part of the same network and therefore needs to be subject to the same levels of protection, not only to protect the computer but the network. In the EndPoint Control section you can set the minimum standards for things like AntiVirus software and VPN software.

Proxy option components

Any time a security profile that requires the use of a proxy is enabled the Proxy Options field will be displayed. Certain inspections defined in security profiles require that the traffic be held in proxy while the inspection is carried out and so the Proxy Options are there to define the parameters of how the traffic will be processed and to what level the traffic will be processed. In the same way that there can be multiple security profiles of a single type there can also be a number of unique Proxy Option profiles so that as the requirements for a policy differ from one policy to the next you can also configure a different Proxy Option profile for each individual policy or you can use one profile repeatedly.

The Proxy Options refer to the handling of the following protocols:

  • HTTP
  • SMTP
  • POP3
  • IMAP
  • FTP
  • NNTP
  • MAPI
  • DNS
  • IM

The configuration for each of these protocols is handled separately.

It should also be noted that these configurations apply to only the Security Profiles Proxy-based processes and not the Flow-based processes.

The use of different proxy profiles and profile options

Just like other components of the FortiGate, there is the option for different Proxy Option profiles so that you can be very granular in your control of the workings of the FortiGate. In the case of the Proxy Option profiles the thing that you will want to focus on is the matching up of the correct profile to a firewall policy that is using the appropriate protocols. If you are creating a Proxy Option profile that is designed for policies that control SMTP traffic into your network you only want to configure the settings that apply to SMTP. You do not need or want to configure the HTTP components.

Oversized file log

This setting is for those that would like to log the occurrence of oversized files being processed. It does not change how they are processed it only enables the FortiGate unit to log that they were either blocked or allowed through. A common practice is to allow larger files through without antivirus processing. This allows you to get an idea of how often this happens and decide on whether or not to alter the settings relating to the treatment of oversized files.

The setting of the threshold for what is considered to be an oversized file is located in the Oversized File / Email Threshold that is found in some of the protocol options for the Proxy Options.

Protocol port mapping

While each of the protocols listed has a default TCP port that is commonly used, the level of granularity of control on the FortiGate firewall allows that the port used by the protocols can be individually modified in each separate Profile. It can also be set to inspect any port with flowing traffic for that particular protocol. The headers of the packets will indicate which protocol generated the packet. To optimize the resources of the unit the mapping and inspection of protocols can be enabled or disabled depending on your requirments.

Comfort Clients

When proxy-based antivirus scanning is enabled, the FortiGate unit buffers files as they are downloaded. Once the entire file is captured, the FortiGate unit begins scanning the file. During the buffering and scanning procedure, the user must wait. After the scan is completed, if no infection is found, the file is sent to the next step in the process flow. If the file is a large one this part of the process can take some time. In some cases enough time that some users may get impatient and cancel the download.

The comfort client feature to mitigates this potential issue by feeding a trickle of data while waiting for the scan to complete so as to let the user know that processing is taking place and that there hasn’t been a failure in the transmission. This slow transfer rate continues until the antivirus scan is complete. Once the file has been successfully scanned without any indication of viruses the transfer will proceed at full speed.

If there is evidence of an infection the FortiGate unit caches the URL and drops the connection. The client does not receive any notification of what happened because the download to the client had already started. Instead, the download stops and the user is left with a partially downloaded file. If the user tries to download the same file again within a short period of time, the cached URL is matched and the download is blocked. The client receives the Infection cache message replacement message as a notification that the download has been blocked. The number of URLs in the cache is limited by the size of the cache.

Client comforting is available for HTTP and FTP traffic. If your FortiGate unit supports SSL content scanning and inspection, you can also configure client comforting for HTTPS and FTPS traffic.

Buffering the entire file allows the FortiGate unit to eliminate the danger of missing an infection due to fragmentation because the file is reassembled before examination. Client comforting can send unscanned and therefore potentially infected content to the client. You should only enable client comforting if you are prepared to accept this risk. Keeping the client comforting interval high and the amount low will reduce the amount of potentially infected data that is downloaded.

Oversized file/email threshold

This is another feature that is related to antivirus scanning. The FortiGate unit has a finite amount of resources that can be used to buffer and scan a file. If a large file such as an ISO image or video file was to be downloaded this could not only overwhelm the memory of the FortiGate, especially if there were other large files being downloaded at the same time, but could exceed it as well. For this reason, how to treat large files needs to be addressed.

A threshold is assigned to determine what should be considered an oversize file or email. This can be set at any size from 1 MB to 50 MB. Any file or email over this threshold will not be processed by the Antivirus Security Profiles. Once a file is determined to be oversized it must be then determined whether to allow it or to block it.

These settings are not a technical decision but a policy one that will depend on your comfort level with letting files into your network. As there often is, there is a compromise between convenience or ease of use and security. If you want to go for a high peace of mind level you can configure the firewall to block oversized files and thus no files would be coming into the network that have not been scanned. If you are looking for optimizing the memory of the FortiGate unit and making sure that everybody is getting the files they want, you can lower the threshold and allow files that are over the threshold.

It should be noted that in terms of probability that malware is more likely to be found in smaller files than in larger files. A number of administrators take this into account when they lower the default threshold so as to lessen the impact on memory if they see the FortiGate unit going into conserve mode on a regular basis.

Chunked bypass

The HTTP section allows the enabling of “Chunked Bypass”. This refers to the mechanism in version 1.1 of HTTP that allows a web server to start sending chunks of dynamically generated output in response to a request before actually knowing the actual size of the content. Where dynamically generated content is concerned this means that there is a faster initial response to HTTP requests. From a security stand point it means that the content will not be held in the proxy as an entire file before proceeding.

Allow fragmented messages

The specifications of RFC 2046 allow for the breaking up of emails and sending the fragments in parallel to be rebuilt and read at the other end by the mail server. It was originally designed to increase the performance over slower connections where larger email messages were involved. It will depend on your mail configuration if this is even possible for your network but outside of Microsoft Outlook and Outlook Express, not many email clients are set up to break up messages like this. The drawback of allowing this feature is that if malware is broken up between multiple fragments of the message the risk is run that it will not be detected by some antivirus configurations because the code may not all be present at the same time to identify.

Append email signature

The Append Email Signature is used when an organization would like to ensure that over and above our in this case underneath the existing personal signatures of the sender, all of the emails going out of their network have the appropriate “boilerplate”, for lack of a better term. These appended emails do not replace existing signatures. They are as the feature states, appended to the email.

Examples could include things like:

  • Without prior approval the email should not be forwarded.
  • Please be environmentally friendly and don’t print out emails
  • For questions regarding the purchasing of our products please call...

It can be anything that the organization would like as long as it is in text format. The use of this feature usually works best in an environment where there is some standardization of what goes into the personal signatures of the senders so that there is no duplication or contradiction of information in the signatures.