Sirius escaped Azkaban and he's coming back and I'm worried that he's going to hurt me.
This is when Harry, Ron, and Hermoine are on the way to Hogwarts for the first time. Ron has his rat, Scabbers, which represents the Socially Engineering Trojan.
Stop! That's not a rat, it's Peter Pettigrew.
What? You're crazy!
Ron always kept Scabbers with him.
See? I told you! How long have you had him?
When Harry found out that Sirius was coming back, Scabbers overheard. This was sensitive information that no one was supposed to find out. This represents how a Socially Engineering Trojan can get information by posing as someone else.
Oh no! He must have heard a lot that he shouldn't have.
Sirius accuses Scabbers of being Peter Pettigrew, he is being wary and making sure that he doesn't fall for anything which is one way to prevent Socially Engineering Trojan attacks.
Sirius was right and Scabbers turns back into Peter Pettigrew. This represents how Socially Engineering Trojans can pose as someone else to manipulate people into giving them what they want.
Socially Engineering Trojans are people who have learned the art of manipulating other people. In this story, Peter Pettigrew was disguised as a rat and heard a lot of Ron's conversations that contained information that no one else was supposed to hear.