It is the second time such gruesome footage has been released by Ansar Beit al-Maqdis (Partisans of Jerusalem), the deadliest militant group based in Egypt's insurgency-hit Sinai region.
A similar video of beheadings was released by the group on August 28, showing the decapitation of four men also accused of being "Israeli informants".
Ansar Beit al-Maqdis says it supports the Islamic State (IS) group which has seized swathes of territory in Iraq and Syria, but has not pledged formal allegiance to it.
Sunday's video, released on Twitter, features parts of a September speech by IS spokesman Abu Mohamed al-Adnani directed at Sinai jihadists, urging them to kill Egyptian security personnel.
The footage then shows the execution of four men after their recorded "confessions".
One was shot dead after saying he worked with the Egyptian army, while the other three were beheaded after saying they worked for Mossad.
Before being killed, the men called on other "spies" to repent publicly, saying the militants knew who they were and that they would not be spared.
The footage also shows jihadists manning checkpoints and searching for "spies".
Egypt's Sinai Peninsula bordering Israel has seen fighting between militants and security forces after the army ousted Islamist president Mohamed Morsi in July last year.
Militants have killed scores of security personnel, saying the attacks are in retaliation for a brutal government crackdown since Morsi 's ouster.
The authorities have launched a sweeping crackdown on his supporters which has left at least 1,400 people dead and more than 15,000 jailed.