VoIP and Internet phone call became major thing in recent years. But this can not hide fact, that security is not strong in nowadays VoIP products. This is due fact almost all (SIP, RTP) voice related protocols are not encrypted. This means everyone can put it own “ear” and listen what You are talking. Probably for most users it is acceptable risk (taking it versus low or no price for connection) but in some cases it is not. Especially when using in business, You would like to be sure that Your conversations remains private. In such case maybe ZFONE from Phill Zimmermann (do You remember PGP?) will do for You.