Tax season is open season for cybercriminals and phishers, who increase their efforts to obtain personal information and Social Security numbers in the run up to – and during – tax season. Until April, we can expect many W2 phishing attacks. Make sure you are prepared and do not fall for a scam.
Anatomy of a W2 Phishing Attack
The most common method of stealing the information needed to file fraudulent tax returns is phishing. Phishing emails are sent in the millions to individuals in an effort to obtain their sensitive information. Individuals must be on high alert for malicious emails during tax season, but it is businesses that are most likely to be targeted.
Payroll employees have access to the W2 forms of the entire workforce. If a single worker can be convinced to email the data, the attacker can file thousands of fraudulent tax returns in the names of employees.
The way cybercriminals get payroll staff to part with sensitive data is by impersonating the CEO or CFO in what is referred to as a Business Email Compromise Scam – otherwise known as a BEC attack or CEO fraud.
The most successful attacks require access to the CEO or CFO’s email account to be gained. That means the CEO or CFO must first be targeted with a spear phishing email and lured into parting with his/her login credentials. Once access to the email account is gained, the impostor can craft an email and send it to a select group of individuals in the company: Payroll and accounts department employees.
The company is researched, individuals likely to have access to W2 forms are identified, and emails are sent. A request is made to attach the W2 forms of all employees who worked for the company in the past year, or for a specific group of employees. A series of emails may be sent, rather than asking for the information straight away.
Since the attacker has access to the CEO’s or CFO’s email account, they can delete sent emails and replies before they are seen by the account holder.
An alternative way of conducting BEC attacks is to spoof an email address. The CFO or CEO is identified from social media sites or LinkedIn, the email address is obtained or guessed based on the format used by the company, and the email is made to appear as if it has come from that email account. An alternative is for the attacker to purchase a similar domain to that used by the company, with two transposed letters for instance. Enough to fool an inattentive worker.
Oftentimes, W2 phishing attacks are not detected until days or weeks after the W2 forms have been sent, by which times IRS tax refund checks have been received and cashed.
How to Defend Against W2 Phishing Attacks
There are several methods that can be used to block W2 phishing attacks. A software or cloud-based anti-spam service should be used to block attacks that come from outside the company. Configured correctly, the spam filter should block spoofed emails and emails sent from similar domains to that used by the company. However, a spam filter will not block emails that come from the CFO or CEOs account.
Multi-factor authentication should be set up on all email accounts to help prevent the first phish that gives the attacker access to a C-suite email address. W2 phishing attacks using spoofed email addresses are much easier to identify and block.
It is therefore important to raise awareness of the threat of W2 phishing attacks with accounts and payroll staff, and anyone else with access to W2 forms. Training can greatly reduce susceptibility to W2 phishing attacks. Training should also be provided to the C-suite, not just employees.
The number of staff who have access to W2 forms should be restricted as far as is possible. Policies should also be introduced that require any request for W2 data to be verified. At a minimum, a request for the data should be checked by a supervisor. Ideally, the request should be confirmed face to face with the sender of the email, or with a quick phone call. The scammers rely on this check not taking place.