One of the main threats in the area of in frastructure security is the physical access to the network devices. For example, in alarge airport it’s impossible to guarantee
the physical inaccessibility to the network devices. Once the intruder gains a physical access to the device, he/she can modify, replace the internal firmware of that device.
An intruder can gain access to the network cabling as well. This is another example of the threat in this area. It is impossible to completely prevent such accesses. For example if a provider needs to exchange some network equipment in their network, no one can guarantee that the equipment on its way from a factory to the provider location was not modified.