On-line banking offers a significant money laundering risk to a financial institution because:
The nature of on-line banking can make it difficult to establish who is controlling the account. On-line banking allows customers to access their accounts remotely, without face-to-face contact with the financial institution. This can pose challenges for verifying the identity and legitimacy of the account holder, especially if the account is opened on-line or through a third-party intermediary. On-line banking can also facilitate the use of anonymous or fictitious identities, or the use of proxies or nominees to hide the true beneficial owner of the account.
The ease of access through the internet enables cross border movement of funds. On-line banking allows customers to transfer funds quickly and easily across different jurisdictions, without physical movement of cash or other instruments. This can increase the risk of money laundering, as funds can be moved to or from high-risk countries or regions, or through multiple accounts or financial institutions, to obscure the origin, destination, or purpose of the funds. On-line banking can also enable customers to access or use alternative payment systems or virtual currencies, which may have lower regulatory oversight or transparency standards than traditional banking systems.
The speed of electronic transaction enables execution of multiple complex transactions within short time frame. On-line banking allows customers to conduct transactions in real time, with minimal or no human intervention or verification. This can increase the risk of money laundering, as customers can execute multiple transactions in a short period of time, or use complex transaction structures or patterns, to avoid detection or reporting thresholds, or to conceal the source, nature, or ownership of the funds. On-line banking can also enable customers to use automated or algorithmic trading systems, which may generate large volumes of transactions that are difficult to monitor or analyze.
CAMS Study Guide - 6th Edition, Chapter 5, pages 139-140
CAMS Certification Exam Outline, Domain 2, Task 2.1, Skill 2.1.1
Online Banking and Money Laundering, ACAMS Today, September 2012

According to the research report by the Council of Europe1, one of the typologies of money laundering through online gambling is the use of multiple accounts and identities to conceal the source and destination of funds. This can be done by opening several accounts under the same name using different IP addresses, or by using false or stolen identification documents to create multiple accounts. Another typology is the use of online gambling platforms that are not regulated or authorized by the jurisdiction where the customer is located, or that do not require know-your-client information from users. This can allow money launderers to access the online gambling services from multiple countries, without being subject to any verification or monitoring by the authorities.
1: Research report - The use of online gambling for money laundering and the financing of terrorism purposes, Council of Europe, April 2013.

According to the Basel Committee on Banking Supervisionprinciples, one of the core principles for effective banking supervision is that the supervisor determines that banks have adequate policies and processes for identifying, assessing and managing the risk and impact of exposures to and transactions with related parties, and that these policies and processes are effectively implemented1. Failure to conduct proper due diligence on a close relative of a senior manager who requests to open an account posesthe highest operational risk, as it could result in conflicts of interest, reputational damage, legal liability, or financial losses for the bank. The other options are not necessarily the highest operational risk, as they depend on the nature and extent of the relationship, the type and size of the account, and the regulatory and legal framework of the jurisdiction.
1 Core principles for effective banking supervision, Principle 20.

According to the Anti-Money Laundering Specialist (the 6th edition) resources, the employee should report the conversation to the compliance officer because the colleague is engaging in tipping off, which is a serious violation of anti-money laundering laws and regulations. Tipping off is the act of informing a person or entity that they are the subject of a suspicious transaction report or an investigation, or providing any information that may compromise or impede the investigation. Tipping off can result in criminal penalties, civil liabilities, and disciplinary actions for the individual and the institution. Therefore, the employee has a duty to report the colleague's misconduct to the compliance officer, who is responsible for ensuring compliance with the anti- money laundering policies and procedures, and taking appropriate corrective actions.
CAMS Certification Package - 6th Edition | ACAMS, Chapter 3: Compliance Standards for Anti-Money Laundering (AML) and Combating the Financing of Terrorism (CFT), page 97 CAMS Certifications: How to Get CAMS Certified | ACAMS, CAMS Examination Preparation, page 8 ACAMS CAMS Certification Video Training Course - Exam-Labs, Module 3: Compliance Standards for Anti-Money Laundering and Combating the Financing of Terrorism, video 3.4: Tipping Off and Confidentiality Exam CAMS: Certified Anti-Money Laundering Specialist (the 6th edition), Question 8, Answer B