Social engineering is the manipulation of people to perform actions or divulge confidential information. It is a common technique used by attackers to gain unauthorized access to systems or data. Employees who use public social networking sites may be vulnerable to social engineering attacks, such as phishing, baiting, or pretexting, which pose the greatest risk to the organization's security. The other options are not as serious as social engineering, as they relate to web application vulnerabilities, intellectual property rights, and reputation management, which are less likely to compromise the organization's assets or operations. References: CISA Review Manual (Digital Version), Domain 5: Protection of Information Assets, Section 5.3 Security Awareness Training1

The greatest risk associated with storing customer data on a web server is data confidentiality. Data confidentiality is the property that ensures that data are accessible only to authorized entities or individuals, and protected from unauthorized disclosure or exposure. Storing customer data on a web server poses a high risk to data confidentiality, as web servers are exposed to the internet and may be vulnerable to various types of attacks or breaches that can compromise the security and privacy of customer data, such as hacking, phishing, malware, denial of service (DoS), etc. Customer data may contain sensitive or personal information that can cause harm or damage to customers or the organization if disclosed or exposed, such as identity theft, fraud, reputation loss, legal liability, etc. Data availability is the property that ensures that data are accessible and usable by authorized entities or individuals when needed. Data availability is a risk associated with storing customer data on a web server, as web servers may experience failures or disruptions that can affect the accessibility and usability of customer data, such as hardware faults, network issues, power outages, etc.
However, data availability is not the greatest risk associated with storing customer data on a web server, as it does not affect the security and privacy of customer data. Data integrity is the property that ensures that data are accurate and consistent, and protected from unauthorized modification or corruption. Data integrity is a risk associated with storing customer data on a web server, as web servers may be subject to attacks or errors that can affect the accuracy and consistency of customer data, such as injection attacks, tampering, replication issues, etc. However, data integrity is not the greatest risk associated with storing customer data on a web server, as it does not affect the security and privacy of customer data. Data redundancy is the condition of having duplicate or unnecessary data in a database or system. Data redundancy is not a risk associated with storing customer data on a web server, but rather a result of poor database design or management.

A change log is a record of all changes made to a system or application, including the date, time, description, and approval of each change. A change log can help an IS auditor to trace the source and authorization of a modification to a system's security settings. A system event correlation report is a tool that analyzes data from multiple sources to identify patterns and anomalies that indicate potential security incidents. A database log is a record of all transactions and activities performed on a database, such as queries, updates, and backups. A security incident and event management (SIEM) report is a tool that collects, analyzes, and reports on data from various sources to detect and respond to security incidents.