## 8 Taxonomy of Ad Fraud Prevention and Detection Methods
### Detection of Digital Advertising Fraud by Commercial Companies  
Advertising technology companies are aware that click fraud and impression fraud are the most dominant fraud activities in online ad systems; therefore, they mostly offer services in detecting these two types of fraud.  
Oxford Biochron [74] is an example of a fraud detection and verification company that focuses on the activity after the click leading up to the purchase event. They work to find well-disguised fraud targeting affiliate and lead generation advertising campaigns. DoubleVerify (DV) Inc. (New York, NY, USA) [75] is another prominent ad tech company that deploys cookies and fingerprint tracking methods in analyzing impressions. They help publishers deliver high quality traffic to their clients. Furthermore, DSPs and Ad exchanges can benefit from authentication techniques that DV offers to validate pre-bid decisions based on their inventories' quality (the DV solution determines whether the inventory is having an impact on customers. DV delivers an in-depth look at viewability metrics throughout the inventory, with consistent measurement across platforms, devices, and formats, assisting advertisers in delivering value and performance). DV takes snapshots of web pages and their advertisements and compares them to the graphical content extracted from HTML codes to detect invisible advertisements. They also apply a geometric analysis system to check the viewability of online advertisements. This method calculates the ads' location and the location of viewable areas of the browsers to discern stuffing or stacking fraud in the ad ecosystem. WhiteOps [76] is a pioneer among bot fighting ad tech companies, and it has designed FraudSensor (a JavaScript-based detection tag) and MediaGuard (real-time preventive technology with the global footprint of evidence-based intelligence) to detect bot traffic. In particular, these products eliminate non-human traffic from publishers' inventory and help them sell their inventory without fear of getting blocked. IAS (Integral Ad Science) [77], a media valuation company, addresses ad fraud, ad viewability, and brand risk issues and verifies online ad placement quality for both publishers and advertisers. IAS provides a particular service called 'True Advertising Quality', which scores sellers and buyers based on the metrics such as brand safety, ad fraud, content, structure, and viewability. Pixalate [78] delivers the following services to the parties in the digital advertising ecosystem: (1) they can detect non-human traffic in real-time and (2) they monitor almost 50 million URLs while preventing 15 types of ad fraud. They combine various methods such as viewability, domain masking and ads.txt file quality to protect online advertising parties against fraudsters. Forensiq by Impact [79] provides a fraud detection system that identifies malicious activities and eliminates bad actors to ensure that only quality traffic is being driven to the publisher's inventory. Forensiq technology has benefited from machine learning techniques to offer the best in class bot-traffic identification and ensure better ad viewability, ad placement, and brand safety. ClickGUARD [80] is a well-known company that tries to prevent and detect click fraud. ClickGUARD offers a real-time monitoring system for all incoming traffic to instantly monitor every visitor's source, network, and post-click behavior details as clicks happen on the ads. The system analyses the visitor behavior characteristics of every click against common fraud patterns. Moat Inc. (New York, NY, USA) [81] performs real-time ad analytics and offers various ad performance metrics to validate ad impressions and assessaudiences. These metrics include: viewability assessment, non-human traffic detection, audience characterization, audience attention and engagement evaluation.