IBM said Wednesday it will spend $1.3 billion in cash to <A HREF="http://news.yahoo.com/s/ap/20060823/ap_on_hi_te/ibm_internet_security_systems">acquire Internet Security Systems,</A> which performs network monitoring and analysis services for companies. The deal values ISS at $28 a share, an 8 percent premium to ISS's close at $26 on Tuesday on the Nasdaq Stock Market. If the acquisition is approved by shareholders, the companies expect it to close in the fourth quarter.