Section: Protection of Information Assets
Explanation:
Collusion is an active attack that can be sustained and is difficult to identify since even well-thought-out application controls may be circumvented. The other choices do not impact well-designed application controls.

Explanation
The greatest risk if two users have concurrent access to the same database record is data integrity. Data integrity is the property that ensures that the data is accurate, complete, consistent, and valid throughout its lifecycle. If two users have concurrent access to the same database record, they may modify or delete the data in a conflicting or inconsistent manner, resulting in data corruption, loss, or duplication. This can affect the reliability and quality of the data, and cause errors or anomalies in the database operations and functions. The IS auditor should verify that the database has adequate controls to prevent or resolve concurrent access issues, such as locking mechanisms, transaction isolation levels, concurrency control protocols, or timestamping methods. References: CISA Review Manual (Digital Version)1, Chapter 5, Section 5.2.7

Explanation/Reference:
In one way authentication only server needs to be authenticated where as in mutual authentication both the client and the server needs to be authenticated.
For CISA exam you should know the information below about Secure Socket Layer (SSL) and Transport Layer Security (TLS) These are cryptographic protocols which provide secure communication on Internet. There are only slight difference between SSL 3.0 and TLS 1.0. For general concept both are called SSL.
SSL is session-connection layer protocol widely used on Internet for communication between browser and web servers, where any amount of data is securely transmitted while a session is established. SSL provides end point authentication and communication privacy over the Internet using cryptography. In typical use, only the server is authenticated while client remains unauthenticated. Mutual authentication requires PKI development to clients. The protocol allows application to communicate in a way designed to prevent eavesdropping, tampering and message forging.
SSL involves a number of basic phases
Peer negotiation for algorithm support
Public-key, encryption based key exchange and certificate based authentication Symmetric cipher based traffic encryption.
SSL runs on a layer beneath application protocol such as HTTP, SMTP and Network News Transport Protocol (NNTP) and above the TCP transport protocol, which forms part of TCP/IP suite.
SSL uses a hybrid hashed, private and public key cryptographic processes to secure transmission over the INTERNET through a PKI.
The SSL handshake protocol is based on the application layer but provides for the security of the communication session too. It negotiates the security parameter for each communication section. Multiple session can belong to one SSL session and the participating in one session can take part in multiple simultaneous sessions.
The following were incorrect answers:
The other choices presented in the options are not valid as in one way authentication only server needs to be authenticated where as client will remain unauthenticated.
The following reference(s) were/was used to create this question:
CISA review manual 2014 Page number 352

Transaction authorization is the primary security concern for EDI environments.