Multiple backdoors were discovered within the OS used on Juniper network devices which allows an attacker to monitor and alter all network traffic. The backdoor is believed to come from a big nation funded operation and mainly not only shows the obvious malicious infiltration of global network infrastructure but also the danger in the nature of these kind of backdoors as well as when they become public, even more malicious actors can abuse them to cause damage.
archived source: https://wellthissucks.xyz/2015/12/18/backdoor-in-juniper-network-devices-archived-source/