What tricks and means of security may be adopted

Narrated Jabir:

The Prophet ﷺ said, "Who is ready to kill Ka'b bin Ashraf (i.e. a Jew)." Muhammad bin Maslama replied, "Do you like me to kill him?" The Prophet replied in the affirmative. Muhammad bin Maslama said, "Then allow me to say what I like." The Prophet replied, "I do (i.e. allow you)."

حَدَّثَنِي عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، حَدَّثَنَا سُفْيَانُ، عَنْ عَمْرٍو، عَنْ جَابِرٍ، عَنِ النَّبِيِّ ﷺ قَالَ " مَنْ لِكَعْبِ بْنِ الأَشْرَفِ ". فَقَالَ مُحَمَّدُ بْنُ مَسْلَمَةَ أَتُحِبُّ أَنْ أَقْتُلَهُ قَالَ " نَعَمْ ". قَالَ فَأْذَنْ لِي فَأَقُولَ. قَالَ " قَدْ فَعَلْتُ ".