When an IS audit reveals that a firewall was unable to recognize a number of attack attempts, the auditor's best recommendation is to place an intrusion detection system (IDS) between the firewall and the Internet, as this would provide an additional layer of security and alert the organization of any malicious traffic that bypasses or penetrates the firewall. Placing an IDS between the firewall and the demilitarized zone (DMZ), the organization's web server, or the organization's network would not be as effective, as it would only monitor the traffic that has already passed through the firewall. References: CISA Review Manual (Digital Version), Chapter 5, Section 5.4.3

The correct answer is C. Software escrow agreement. A software escrow agreement is a legal arrangement between three parties: the software developer (licensor), the end-user (licensee), and an escrow agent. The agreement ensures that the software's source code and other relevant assets are securely stored with the escrow agent, and can be released to the licensee under certain conditions, such as the licensor's bankruptcy, insolvency, or failure to provide support or maintenance1. A software escrow agreement can provide the licensee with assurance and continuity for the software they depend on, and protect them from losing access or functionality in case of any unforeseen events or disputes with the licensor1.