It is highly dangerous to download firewall software from unverified third-party sources. A firewall is your network's first line of defense. A modified ISO could contain backdoors, keyloggers, or rootkits that compromise your entire network security. If you cannot verify the checksum against the official Netgate documentation, do not use the file.
: Best for installing on virtual machines (VMs) or hardware via a physical or virtual optical drive. pfsense 251 download iso link
While pfSense 2.5.1 was a robust firewall solution in its time, it is now considered regarding active support and primary distribution. It is highly dangerous to download firewall software
The 2.5.1 release of pfSense comes with a plethora of enhancements and features designed to improve performance, security, and usability. Some of the notable features include: pfsense 251 download iso link