Category: academic articles

Academic articles

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The Dark Underbelly of Online Advertising

Edelman, Benjamin. “The Dark Underbelly of Online Advertising.” HBR Now. (November 17, 2009).

The Internet is sold to advertisers as a highly measurable medium that is the most efficient way to target exactly the right customers. But online advertising is also easily subverted–letting fraudsters claim advertising fees for work they did not actually do. The trickiest frauds deceive advertisers so effectively that measurements of ad effectiveness report the fraudsters as exceptionally productive and high quality, rather than revealing that their traffic was actually worthless. This is a quiet scandal. In a time of tightening ad budgets, losses to advertising fraud come straight from the bottom line–but savings can be equally dramatic. Here’s a look behind the veil–an explanation of ad practices that have cheated even the Web’s largest advertisers. Advertising scams take plenty of victims, both witting and not, but I offer strategies to help determined marketers protect themselves.

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Deterring Online Advertising Fraud Through Optimal Payment in Arrears

Edelman, Benjamin. “Deterring Online Advertising Fraud Through Optimal Payment in Arrears.” Financial Cryptography and Data Security: Proceedings of the International Conference (September 2009). (Springer-Verlag Lecture Notes in Computer Science.) (Featured in Working Knowledge: Reducing Risk with Online Advertising.)

Online advertisers face substantial difficulty in selecting and supervising small advertising partners. Fraud can be well hidden, and limited reputation systems reduce accountability. But partners are not paid until after their work is complete, and advertisers can extend this delay both to improve detection of improper partner practices and to punish partners who turn out to be rule-breakers. I capture these relationships in a screening model with delayed payments and probabilistic delayed observation of agents’ types. I derive conditions in which an advertising principal can set its payment delay to deter rogue agents and to attract solely or primarily good-type agents. Through the savings from excluding rogue agents, the principal can increase its profits while offering increased payments to good-type agents. I estimate that a leading affiliate network could have invoked an optimal payment delay to eliminate 71% of fraud without decreasing profit.

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Priced and Unpriced Online Markets

Edelman, Benjamin. “Priced and Unpriced Online Markets.” Journal of Economic Perspectives 23, no. 3 (Summer 2009): 21-36.

With forces both supporting and opposing zero prices, typical Internet-related activities–like surfing the web, web searches, and e-mail, along with behind-the-scenes practices like domain names and the allocation of IP (Internet Protocol) addresses–present a natural context to reevaluate our sense of the tradeoffs that arise between free and a positive price. In this piece, I offer a series of specific examples of resources offered without charge, for a positive price, or for a flat fee (“all-you-can-eat”). I conclude by assessing the characteristics that shape pricing structure for these resources.

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Securing Online Advertising: Rustlers and Sheriffs in the New Wild West

Edelman, Benjamin. “Securing Online Advertising: Rustlers and Sheriffs in the New Wild West.” In Beautiful Security, edited by Andy Oram and John Viega. O’Reilly Media, Inc., 2009. (Korean translation.)

Read the news of recent computer security guffaws, and it’s striking how many problems stem from online advertising. Advertising is the bedrock of web sites that are provided without charge to end users, so advertising is everywhere. But advertising security gaps are equally widespread: from “malvertisement” banner ads pushing rogue anti-spyware software, to click fraud, to spyware and adware, the security lapses of online advertising are striking.

During the past five years, I have uncovered hundreds of online advertising scams defrauding thousands of users–not to mention all the web’s top merchants. This chapter summarizes some of what I’ve found–and what users and advertisers can do to protect themselves.

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Running Out of Numbers? The Impending Scarcity of IP Addresses and What To Do About It

Edelman, Benjamin. “Running Out of Numbers: Scarcity of IP Addresses and What To Do About It.” Auctions, Market Mechanisms and Their Applications 14 (2009): 95-106. (Springer-Verlag Lecture Notes of the Institute for Computer Science.) (Featured in Working Knowledge: When the Internet Runs Out of IP Addresses) (Circulated in 2008 as Running Out of Numbers? The Impending Scarcity of IP Addresses and What To Do About It.)

The Internet’s current numbering system is nearing exhaustion: Existing protocols allow only a finite set of computer numbers (“IP addresses”), and central authorities will soon deplete their supply. I evaluate a series of possible responses to this shortage: Sharing addresses impedes new Internet applications and does not seem to be scalable. A new numbering system (“IPv6”) offers greater capacity, but network incentives impede transition. Paid transfers of IP addresses would better allocate resources to those who need them most, but unrestricted transfers might threaten the Internet’s routing system. I suggest policies to create an IP address “market” while avoiding major negative externalities–mitigating the worst effects of v4 scarcity, while obtaining price discovery and allocative efficiency benefits of market transactions.

Disclosure: I provide advice to ARIN’s counsel on matters pertaining to v6 transition, v4 exhaustion, and possible revisions to ARIN’s v4 transfer policy. But this paper expresses only my own views – not the views of ARIN, its Board, or its staff. I write on my own behalf, not for ARIN, nor at ARIN’s instruction or request.

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Adverse Selection in Online ‘Trust’ Certifications

Edelman, Benjamin. “Adverse Selection in Online ‘Trust’ Certifications.” Proceedings of the International Conference on Electronic Commerce (2009): 205-212. (ACM International Conference Proceeding Series.)

Widely used online “trust” authorities issue certifications without substantial verification of recipients’ actual trustworthiness. This lax approach gives rise to adverse selection: the sites that seek and obtain trust certifications are actually less trustworthy than others. Using a new dataset on web site safety, I demonstrate that sites certified by the best-known authority, TRUSTe, are more than twice as likely to be untrustworthy as uncertified sites. This difference remains statistically and economically significant when restricted to “complex” commercial sites. In contrast, competing certification system BBBOnline imposes somewhat stricter requirements and appears to provide a certification of positive, albeit limited, value.

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CPC/CPA Hybrid Bidding in a Second Price Auction

Edelman, Benjamin, and Hoan Lee. “CPC/CPA Hybrid Bidding in a Second Price Auction.” Harvard Business School Working Paper, No. 09-074, December 2008.

We develop a model of online advertising in which each advertiser chooses from multiple advertising measurement metrics–paying either for each click on its ads (CPC), or for each purchase that follows an ad-click (CPA). Our analysis extends classic auction results by allowing players to make bids using two different pricing schemes, while the driving information for bidders’ endogenous selection–the conversion rate–is hidden from the seller. We show that the advertisers with the most productive sites prefer to pay CPC, while advertisers with lower quality sites prefer to pay CPA–a result that may be viewed as counterintuitive since low quality sites cannot proudly tout their conversion rates. This result holds even if an ad platform’s assessment of site quality is correct in expectation. We also show that by offering both CPC and CPA, an ad platform can weakly increase its revenues compared to offering either alternative alone.

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Typosquatting: Unintended Adventures in Browsing

Edelman, Benjamin. “Typosquatting: Unintended Adventures in Browsing.” Cybercrime Gets Personal, McAfee Security Journal (fall 2008): 34-37.

Typosquatting is the practice of registering domain names, identical to or confusingly similar to trademarks and famous names, in hopes that users will accidentally request these sites–whereupon they will receive, typically, advertisements. This piece presents the basic typosquatting business model, based on my analysis of more than 80,000 typosquatting domain names. I analyze the advertising intermediaries that make typosquatting profitable, and I assess the legislation and litigation that are beginning to put a check on this practice.

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Delaying Payment to Deter Online Advertising Fraud

In a new article, I introduce an alternative method of fraud prevention for certain online advertising systems. By delaying payments, a merchant or network differentially harms bad affiliates (who rightly worry they may get caught) without unduly harming good affiliates (who know they’ll get paid, and who receive a bonus in compensation for the delay). With a suitable delay, a merchant or network can deter many bad affiliates while retaining the good.

My working draft:

Optimal Deterrence when Judgment-Proof Agents are Paid in Arrears – with an Application to Online Advertising Fraud

Details on my approach, including initial data on merchants’ and networks’ current payment terms.

(update: published as Edelman, Benjamin. “Deterring Online Advertising Fraud Through Optimal Payment in Arrears.” Financial Cryptography and Data Security: Proceedings of the International Conference (September 2009). (Springer-Verlag Lecture Notes in Computer Science.))

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On Best-Response Bidding in GSP Auctions

Cary, Matthew, Aparna Das, Benjamin Edelman, Ioannis Giotis, Kurtis Heimerl, Anna R. Karlin, Claire Mathieu, and Michael Schwarz. “On Best-Response Bidding in GSP Auctions.” Harvard Business School Working Paper, No. 08-056, January 2008.

How should players bid in keyword auctions such as those used by Google, Yahoo! and MSN? We model ad auctions as a dynamic game of incomplete information, so we can study the convergence and robustness properties of various strategies. In particular, we consider best-response bidding strategies for a repeated auction on a single keyword, where in each round, each player chooses some optimal bid for the next round, assuming that the other players merely repeat their previous bids. We focus on a strategy we call Balanced Bidding (BB). If all players use the BB strategy, we show that bids converge to a bid vector that obtains in a complete information static model proposed by Edelman, Ostrovsky, and Schwarz. We prove that convergence occurs with probability 1, and we compute the expected time until convergence.