How can you block attackers, who are performing reconnaissance and probing, with nmap and nessus port scanning and vulnerability assessment scanning tools?

 You can block attackers, who are performing reconnaissance and probing, with NMAP and Nessus port scanning and vulnerability assessment scanning tools by identifying the digital signatures of common reconnaissance and probing tools such PING, scans performed by Nmap, Nessus®, etc. The IDS and IPS devices should be programmed to specifically alert and block reconnaissance and probing IP packets that are commonly used by these attack tools.