What does spp_unicode mean?

["protect" <protect () taxcut com>]

Hello:
 
I have just installed DEMARC 1.05 + Snort on Windows 2000 Server and got
number of alerts saying :
 
spp_unicode: Invalid Unicode String Detected
spp_unidecode: Unicode Directory Transversal attack detected
spp_unidecode: CGI Null Byte attack detected
 
and more..
 
Can anyone let me know what does that mean? And from where I can get
more details ton it?
 
Thanks,
 
Protect