Insufficient security According to a US Senate investigation in 2014, there are security and privacy concerns for users due to the infrastructure of online advertising. This is because of the potential for malware to be disseminated through online advertisements and for such
malvertising to be inserted and triggered without sufficient protection or screening.
Ransomware gangs were spotted using carefully targeted Google search advertising to redirect victims to pages dropping malware.
Disinformation and dark money Research published on
New Media & Society shows that several actors abuse the obscurity and complexity of programmatic advertising to spread
disinformation online, for example by directing advertising money to fund
fake news websites. Additionally, the lack of regulation and accountability in the
digital advertising ecosystem has led to the influx of
dark money campaigns that fund
political campaigns without disclosing the source of the funds.
Viewability limitations Eye-tracking studies have shown that Internet users often ignore web page zones likely to contain display ads (sometimes called "
banner blindness"), and this problem is worse online than in offline media. On the other hand, studies suggest that even those ads "ignored" by the users may influence the user subconsciously.
Ad fraud There are numerous ways that advertisers can be overcharged for their advertising. For example,
click fraud occurs when a publisher or third parties click (manually or through automated means) on a CPC ad with no legitimate buying intent. For example, click fraud can occur when a competitor clicks on ads to deplete its rival's advertising budget, or when publishers attempt to manufacture revenue. Online impression fraud can occur when publishers overstate the number of ad impressions they have delivered to their advertisers. To combat impression fraud, several publishing and advertising industry associations are developing ways to count online impressions credibly.
Heterogeneous clients Because users have different operating systems, web browsers and computer hardware (including mobile devices and different screen sizes), online ads may appear to users differently from how the advertiser intended, or the ads may not display properly at all. A 2012
comScore study revealed that, on average, 31% of ads were not "in-view" when rendered, meaning they never had an opportunity to be seen. Rich media ads create even greater compatibility problems, as some developers may use competing (and exclusive) software to render the ads (see e.g.
Comparison of HTML 5 and Flash). Furthermore, advertisers may encounter legal problems if legally required information does not actually display to users, even if that failure is due to technological heterogeneity. In the United States, the FTC has released a set of guidelines indicating that it's the advertisers' responsibility to ensure the ads display any required disclosures or disclaimers, irrespective of the users' technology. Other software programs or browser add-ons may also block the loading of ads, or block elements on a page with behaviors characteristic of ads (e.g. HTML autoplay of both audio and video). Approximately 9% of all online page views come from browsers with ad-blocking software installed, and some publishers have 40%+ of their visitors using ad-blockers. As of Q2 2015, 45 million Americans were using ad blockers. In a survey research study released Q2 2016, Met Facts reported 72 million
Americans, 12.8 million adults in the UK, and 13.2 million adults in
France were using ad blockers on their PCs,
smartphones, or
tablet computers. In March 2016, the
Internet Advertising Bureau reported that UK ad blocking was already at 22% among people over 18 years old. As of 2021, 27% of US Internet users used ad blocking software, a trend that has been increasing since 2014. Among technical audiences the rate of blocking reaches 58% as of 2021.
Anti-targeting technologies Some web browsers offer
privacy modes where users can hide information about themselves from publishers and advertisers. Among other consequences, advertisers can't use cookies to serve targeted ads to private browsers. Most major browsers have incorporated
Do Not Track options into their browser headers, but the regulations currently are only enforced by the
honor system.
Privacy and user surveillance The collection of user information by publishers and advertisers has raised consumer concerns about their privacy. Over half of all
Google and
Facebook users are concerned about their privacy when using Google and Facebook, according to
Gallup. Many consumers have reservations about online
behavioral targeting. By tracking users' online activities, advertisers are able to understand consumers quite well. Advertisers often use technology, such as web bugs and respawning cookies, to maximize their abilities to track consumers. According to a 2011 survey conducted by Harris Interactive, over half of Internet users had a negative impression of online behavioral advertising, and forty percent feared that their personally-identifiable information had been shared with advertisers without their consent. Consumers can be especially troubled by advertisers targeting them based on sensitive information, such as financial or health status. leading to artifices like
phishing (where scam emails look identical to those from a well-known brand owner) and confidence schemes like the
Nigerian "419" scam. The Internet Crime Complaint Center received 289,874 complaints in 2012, totaling over half a billion dollars in losses, most of which originated with scam ads. Consumers also face malware risks, i.e.
malvertising, when interacting with online advertising.
Cisco's 2013 Annual Security Report revealed that clicking on ads was 182 times more likely to install a virus on a user's computer than surfing the Internet for porn. For example, in August 2014 Yahoo's advertising network reportedly saw cases of infection of a variant of
Cryptolocker ransomware.
Spam The Internet's low cost of disseminating advertising contributes to spam, especially by large-scale
spammers. Numerous efforts have been undertaken to combat spam, ranging from blacklists to regulatorily-required labeling to content filters, but most of those efforts have adverse collateral effects, such as mistaken filtering. ==Regulation==