Snape/Filch connection?

[mugglemonkee]

No: HPFGUIDX 86909

As I was rereading Book 1, I noticed that part  just after Halloween where Filch 
is bandaging Snape's leg. 

For some reason it seemed odd to me this time. Did Snape tell the entire staff 
he tried to get by Fluffy, or that he suspected Quirrel, OR did he just tell Filch?

If he did just tell Filch, why? It just seems like a strange choice of person to 
confide in, doesn't it? What is their connection?