What is list bombing, and how can it impact deliverability?

In the past few months, Orita has identified list bombing attacks occurring across 22% of the brands that we’ve reviewed. However, most brands haven’t heard of list bombing, and even fewer understand the potential negative impact it can have on a brand’s deliverability. We’ve put together a comprehensive overview for brands to understand list bombing, and if these attacks are potentially harming their email deliverability.

What is List Bombing?

List bombing is a type of cyber attack where malicious actors subscribe a victim's email address to numerous mailing lists, often thousands, within a short period. This inundates the victim's inbox with a flood of unwanted emails, making it difficult for them to find legitimate emails and potentially causing other issues like email account lockouts.

How Does List Bombing Work?

1. Harvesting Email Addresses: Attackers collect email addresses from data breaches, social media, public directories, or other sources.

2. Automated Subscriptions: Using automated scripts or bots, the attacker subscribes the victim's email address to numerous mailing lists, newsletters, and other subscription services. From Orita’s audits, nearly 20% of brands have mailing lists that are in automated subscription flows.

3. Flooding the Inbox: The victim's inbox is overwhelmed with a massive volume of emails, often coming in faster than they can be manually unsubscribed from.

Consequences of List Bombing

• Inbox Overload: The victim's inbox becomes flooded with unwanted emails, making it challenging to manage legitimate communications.

• Missed Important Emails: Important emails can get lost in the deluge of spam, leading to missed opportunities or critical information, such as order confirmation emails, password reset emails, or other malicious behaviors taken by hackers.

• Email Provider Blacklisting: In extreme cases, the volume of incoming emails can trigger spam filters and cause the email provider to temporarily suspend the account.

• Potential Data Breach: List bombing can sometimes be a precursor to more severe attacks, as attackers may use the chaos to mask phishing attempts or other malicious activities.

Why Do Attackers Use List Bombing?

• Distraction: To distract victims from more targeted attacks such as phishing or fraud.

• Harassment: To harass and inconvenience individuals, often as part of a broader campaign of online harassment.

• Denial of Service: To effectively deny the victim access to their email by making it unusable due to the volume of spam.

Impact of List Bombing on Brands

List bombing attacks don't just affect the victims whose inboxes are flooded with unwanted emails; they also have significant repercussions for the brands whose mailing lists are unwittingly used in these attacks. Here are some key impacts:

Reputation Damage

• Brand Perception: When victims receive a deluge of emails from a brand they did not sign up for, it can lead to negative perceptions of the brand. Recipients might view the brand as spammy or careless about user data.

• Customer Trust: Existing and potential customers may lose trust in the brand if they perceive that the company does not adequately protect their email lists from abuse.

Increased Unsubscribes and Spam Reports

• Higher Unsubscribe Rates: Victims of list bombing are likely to unsubscribe en masse, which can skew a brand's subscriber metrics and affect future marketing efforts.

• Spam Reports: An influx of spam reports can result from list bombing. Email service providers may then flag the brand's emails as spam, affecting deliverability rates to legitimate subscribers.

Email Deliverability Issues

• Blacklisting: If a brand’s emails are reported as spam frequently, the brand's email domain can be blacklisted by email service providers. This can significantly reduce the ability to reach subscribers in the future.

• Deliverability Decline: Overall email deliverability can decline as ESPs (Email Service Providers) and ISPs (Internet Service Providers) become more suspicious of emails from the brand’s domain.

Increased Operational Costs

• Handling Unsubscribes: Managing a sudden spike in unsubscribe requests can be resource-intensive.

• Customer Support: The customer support team may face increased inquiries and complaints related to unwanted emails, necessitating more resources to handle these issues.

Legal and Compliance Risks

• GDPR and CAN-SPAM Violations: If list bombing leads to non-compliance with regulations like GDPR (General Data Protection Regulation) or CAN-SPAM (Controlling the Assault of Non-Solicited Pornography And Marketing), brands may face legal repercussions, including fines and sanctions.

• Privacy Concerns: The misuse of a brand's mailing list in a list bombing attack can raise privacy concerns and lead to scrutiny from regulatory bodies.

Data Quality Issues

• Skewed Analytics: The influx of fake subscribers from list bombing can distort email campaign analytics, making it difficult to measure the effectiveness of marketing efforts.

• Database Hygiene: Cleaning up the email list after an attack requires significant effort to identify and remove bogus sign-ups without inadvertently losing legitimate subscribers.

Mitigation Strategies for Brands

1. Sign up for a free deliverability audit with Orita! Orita actively identifies and removes spam, junk, list-bombing, and non-human actors from your ESP on a daily basis.

2. Implement Strong Subscription Validation: Use CAPTCHA and double opt-in processes to ensure that new subscribers are genuine.

3. Monitor Subscription Activity: Regularly monitor for unusual spikes in subscription activity that could indicate list bombing.

4. Enhanced Email Security: Work with email service providers to implement measures that can detect and mitigate list bombing.

5. Transparent Communication: If a list bombing attack occurs, communicate transparently with your subscriber base to explain the situation and the steps being taken to address it.

6. Regular Audits: Conduct regular audits of your email list to maintain its integrity and remove any suspicious entries.