Exclude Yahoo-Slurp by htaccess?

Hello,

I want to exclude the Yahoo-Bot from indexing pages via htaccess. What Condition should be used?

PS: Yahoo Slurp causes a lot of Traffic and rising Serverloads. There are almost 50-100 Bots online 24h/day!
The advantage isn`t noteworthy...Google and MSN are much better!

Yours, Silmarillion

Use robots.txt

Robots.txt isn`t really able to prevent all Bots from visiting/indexing pages! What about Yahoo Slurp? Will it work?

Yours, Silmarillion

AFAIK, slurp honors robots.txt, and it presents its user agent name upon spidering. If not (can anyone verify this?), you can use the vBulletin admin control panel to exclude the slurp IP block.

@Silmarillion:

Do you have a stats program that allows you to determine what amount of web visitors you are getting from Yahoo?

Just as an example, I have a required profile dropdown field asking users where they found out about the site.

Current stats:

• Google: 37.9%
  
• Friend: 13.5%
  
• Other: 13.5%
  
• Other Web Site: 13.3%
  
• Yahoo!: 12.2%
  
• MSN Search: 4.9%
  
• Other Search Engine: 4.4%