Building security into FortiOS

Building security into FortiOS

The FortiOS operating system, FortiGate hardware devices, and FortiOS virtual machines (VMs) are built with security in mind, so many security features are built into the hardware and software. Fortinet maintains an ISO:9001 certified software and hardware development processes to ensure that FortiOS and FortiGate products are developed in a secure manner

Boot PROM and BIOS security

The boot PROM and BIOS in FortiGate hardware devices use Fortinet’s own FortiBootLoader that is designed and controlled by Fortinet. FortiBootLoader is a secure, proprietary BIOS for all FortiGate appliances. FortiGate physical devices always boot from FortiBootLoader.

FortiOS kernel and user processes

FortiOS is a multi-process operating system with kernel and user processes. The FortiOS kernel runs in a privileged hardware mode while higher-level applications run in user mode. FortiOS is a closed system that does not allow the loading or execution of third-party code in the FortiOS user space. All non-essential services, packages, and applications are removed.

FortiGate appliances with SD drives are encrypted to prevent unauthorized access to data.

Administration access security

Admin administrator account

All FortiGate firewalls ship with a default administrator account called admin. By default, this account does not have a password. FortiOS allows administrators to add a password for this account or to remove the account and create new custom super_admin administrator accounts.

Secure password storage

User and administrator passwords are stored securely on the system in an encrypted format. The encryption hash used for admin account passwords is SHA256/SHA1. The value that is seen in the configuration file is the Base64 encoded hash value. For example:

config system admin edit “admin” set accprofile “super_admin”

set vdom “root”

set password ENC SH2nlSm9QL9tapcHPXIqAXvX7vBJuuqu22hpa0JX0sBuKIo7z2g0Kz/+0KyH4E=

next end

Pre-shared keys in IPSec phase-1 configurations are stored in plain text. In the configuration file these pre-shared keys are encoded. The encoding consists of encrypting the password with a fixed key using DES (AES in FIPS mode) and then Base64 encoding the result.

Maintainer account

Administrators with physical access to a FortiGate appliance can use a console cable and a special administrator account called maintainer to log into the CLI. When enabled, the maintainer account can be used to log in from the console after a hard reboot. The password for the maintainer account is bcpb followed by the FortiGate serial number. An administrator has 60-seconds to complete this login. See Resetting a lost Admin password on the Fortinet Cookbook for details.

The only action the maintainer account has permissions to perform is to reset the passwords of super_admin accounts. Logging in with the maintainer account requires rebooting the FortiGate. FortiOS generates event log messages when you login with the maintainer account and for each password reset.

The maintainer account is enabled by default; however, there is an option to disable this feature. The maintainer account can be disabled using the following command:

config system global set admin-maintainer disable


Administrative access security

Secure administrative access features:

  • SSH, Telnet, and SNMP are disabled by default. If required, these admin services must be explicitly enabled on each interface from the GUI or CLI.
  • SSHv1 is disabled by default. SSHv2 is the default version.
  • SSLv3 and TLS1.0 are disabled by default. TLSv1.1 and TLSv1.2 are the SSL versions enabled by default for HTTPS admin access.
  • HTTP is disabled by default, except on dedicated MGMT, DMZ, and predefined LAN interfaces. HTTP redirect to HTTPS is enabled by default. l The strong-crypto global setting is enabled by default and configures FortiOS to use strong ciphers (AES, 3DES) and digest (SHA1) for HTTPS/SSH/TLS/SSL functions. l SCP is disabled by default. Enabling SCP allows downloading the configuration file from the FortiGate as an alternative method of backing up the configuration file. To enable SCP:

config system global set admin-scp enable


  • DHCP is enabled by default on the dedicated MGMT interface and on the predefined LAN port (defined on some FortiGate models).
  • The default management access configuration for FortiGate models with dedicated MGMT, DMZ, WAN, and LAN interfaces is shown below. Outside of the interfaces listed below, management access must be explicitly enabled on interfaces – management services are enabled on specific interfaces and not globally.
  • Dedicated management interface l Ping l FMG-Access (fgfm) l CAPWAP l HTTPS l HTTP
  • Dedicated WAN1/WAN2 interface l Ping l FMG-Access (fgfm)
  • Dedicated DMZ interface l Ping l FMG-Access (fgfm) l CAPWAP l HTTPS l HTTP
  • Dedicated LAN interface l Ping l FMG-Access (fgfm) l CAPWAP l HTTPS l HTTP

Network security

This section describes FortiOS and FortiGate network security features.

Network interfaces

The following are disabled by default on each FortiGate interface:

l Broadcast forwarding l STP forwarding l VLAN forwarding l L2 forwarding l Netbios forwarding l Ident accept

For more information, see Disable unused protocols on interfaces on page 20.

TCP sequence checking

FortiOS uses TCP sequence checking to ensure a packet is part of a TCP session. By default, anti-replay protection is strict, which means that if a packet is received with sequence numbers that fall out of the expected range, FortiOS drops the packet. Strict anti-replay checking performs packet sequence checking and ICMP antireplay checking with the following criteria:

  • The SYN, FIN, and RST bit cannot appear in the same packet.
  • FortiOS does not allow more than 1 ICMP error packet to go through before it receives a normal TCP or UDP packet.
  • If FortiOS receives an RST packet, FortiOS checks to determine if its sequence number in the RST is within the unACKed data and drops the packet if the sequence number is incorrect. l For each new session, FortiOS checks to determine if the TCP sequence number in a SYN packet has been calculated correctly and started from the correct value.

Reverse path forwarding

FortiOS implements a mechanism called Reverse Path Forwarding (RPF), or Anti Spoofing, to block an IP packet from being forwarded if its source IP does not:

l belong to a locally attached subnet (local interface), or l be in the routing domain of the FortiGate from another source (static route, RIP, OSPF, BGP).

If those conditions are not met, FortiOS silently drops the packet.

FIPS and Common Criteria

FortiOS has received NDPP, EAL2+, and EAL4+ based FIPS and Common Criteria certifications. Common Criteria evaluations involve formal rigorous analysis and testing to examine security aspects of a product or system. Extensive testing activities involve a comprehensive and formally repeatable process, confirming that the security product functions as claimed by the manufacturer. Security weaknesses and potential vulnerabilities are specifically examined during an evaluation.

To see Fortinet’s complete history of FIPS/CC certifications go to the following URL and add Fortinet to the Vendor field:

PSIRT advisories

The FortiGuard Labs Product Security Incident Response Team (PSIRT) continually tests and gathers information about Fortinet hardware and software products, looking for vulnerabilities and weaknesses. Any such findings are fed back to Fortinet’s development teams and serious issues are described along with protective solutions. The PSIRT regulatory releases PSIRT advisories when issues are found and corrected. Advisories are listed at


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This entry was posted in Administration Guides, FortiGate, FortiOS on by .

About Mike

Michael Pruett, CISSP has a wide range of cyber-security and network engineering expertise. The plethora of vendors that resell hardware but have zero engineering knowledge resulting in the wrong hardware or configuration being deployed is a major pet peeve of Michael's. This site was started in an effort to spread information while providing the option of quality consulting services at a much lower price than Fortinet Professional Services. Owns PacketLlama.Com (Fortinet Hardware Sales) and Office Of The CISO, LLC (Cybersecurity consulting firm).

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