Strange User Header

[yaashul]

A strange user identification has accessed more than 500 pages in 15 minute

"Mozilla/5.0 (Windows; N; Microsoft Windows NT 5.1.2600 Service Pack 3; 64Bit:False; .NET CLR 4.0.30319.1) SLFSCore/2.0.0.5 SharpLeech/2.x.x"

Can someone explain what it is?

[wilderness]

"Leech" should be enough to expose their intent.

Another of the derogatory terms that incriminate harvesters and their badly named UA's.

[Pfui]

A quick skim of G's top search result explains what SharpLeech is, and the hit rate you saw explains what it did to you.

What do you do?

For starters, block the Host/IP that just scraped your stuff AND block all UAs containing the word: leech