Inventory Hoarding

Inventory hoarding, also known as inventory denial, is a critical threat faced by web applications, particularly those offering online purchases or reservations. This attack involves hostile bots manipulating inventory, attempting to render it unavailable to genuine customers. For the site owner, this leads to a variety of detrimental consequences.

Attack Scenarios for Inventory Hoarding

Hostile bots attack the targeted sites by beginning, but not completing the sales process. For example, when attacking a retail site, bots add products to shopping carts but (intentionally) do not complete the purchase. Ironically, this tactic is more effective against more sophisticated web applications; basic retail sites often do not update their inventory in real time in response to customer actions, while more advanced sites do. For those that adjust product availability immediately, inventory denial bots create a false scarcity. Their actions reduce the amount of inventory accessible to legitimate customers.

A related threat is a scalping attack, where bots do actually complete the purchases. Here, shopping bots attempt to buy as much inventory as possible, then the attacker resells the products, services, or tickets to the broader market at a (much) higher price. Scalping occurs not only for event tickets, but also rare products, for example limited-edition sneakers and toys.

Industry Vulnerability

Any eCommerce sector that relies on online reservations or purchases, and has limited inventory of the goods or services, is vulnerable to inventory denial. The most obvious are retail and travel, although others can be targeted as well.

Different sectors can attract different kinds of bots. Simple shopping bots can target retail sites, while travel sites often are beset by more sophisticated software. For example, travel applications usually have time-to-checkout policies. The site reserves the tickets (and removes them from available inventory) as customers select them, but the selections expire after an allotted time frame (usually 10-15 minutes) if not purchased. Advanced bots will exploit this; they will begin to make reservations, wait until they expire, and then repeat the process. This continuous loop blocks genuine customers from securing tickets.

Implications of Inventory Hoarding

Financial Loss and Trust Damage:

The obvious financial impact of inventory hoarding is a loss of sales from real customers. But the potential ramifications can extend far beyond blocking legitimate users.

For instance, travel platforms rely on aggregators for data. Every search for flights incurs a small financial liability, commonly known as a data lookup fee. If the searcher completes a purchase, the aggregator earns a commission. However, when bots engage in continuous searches without actual transactions, site owners bear escalating data lookup fees without generating revenue.

The financial toll is not limited to data lookup fees. Sellers can accumulate other expenses due to these malicious activities, significantly impacting their bottom line. Furthermore, the trust and goodwill of consumers are at stake. When legitimate users repeatedly encounter inventory shortages or inflated demand, it can erode their trust in the platform.

Denial-of-Service Impact

Inventory hoarding effectively functions as an Application-Layer Denial-of-Service (DoS) attack. By impeding genuine transactions and creating artificial scarcity, it directly impacts revenue streams. Additionally, time-sensitive inventory might go unsold due to the artificial scarcity created by these attacks. In other situations, such as scalping, consumer anger and significant bad will can result.

Mitigation Strategies against Inventory Hoarding

Time-to-Checkout Policies

Some site owners attempt to address inventory denial attacks with tactics such as adjusting time-to-checkout policies and modifying the duration for completing transactions. While this can mitigate the impact of these incidents, it won’t do much. At best, it will make attacks less effective.

Bot Detection and Mitigation

A web security solution with robust bot detection methods is crucial. Without it, the only indications of an inventory denial attack are worsening conversion rates in the face of increasing traffic.

A good solution will include multiple layers of defense for bot detection and screening, including threat intelligence feeds, blocklisting of known-hostile traffic sources, browser environment verification, UEBA (User and Entity Behavioral Analysis), and more. Advanced algorithms and other tools can distinguish between genuine users and automated traffic, enabling the identification and prevention of inventory hoarding attempts. Continuous monitoring of traffic patterns can detect anomalies and preemptively block suspicious bot activities.

Rate Limiting and Monitoring

In web security, rate limiting refers to the enforcement of maximum rates at which traffic sources can submit requests. This is an important measure for blocking unwanted bots, especially when they engage in activities which generate a lot of traffic. Often, a well-executed inventory denial attack will not generate sufficiently frequent requests to trigger rate limit enforcement. However, rate limiting is still important anyway, not only for inventory hoarding but also for related attacks. For example, scraper bots can have much of the same harmful impact as hoarding bots do, especially for applications that are liable for data lookup fees.

Collaboration and Education

Collaboration within industries to share threat intelligence and best practices is vital. Educating stakeholders about the implications of inventory hoarding attacks can foster a collective effort to combat these threats effectively.

Inventory Hoarding – Summary

Inventory hoarding poses a significant threat to web applications offering online purchasing or reservations, causing financial losses, undermining trust, and impacting user experience. By understanding the mechanisms behind these attacks and implementing proactive measures, businesses can fortify their defenses and safeguard their platforms against such malicious activities.

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