High Conversion Speed is observed when fraudsters provide a high number of fake clicks and convert them into fake installs with a sudden burst. Since the installs are fake, in-app activity is mostly non-existent. Trying to decrease suspicion, clicks may be provided over a longer time. This may also happen when your ad is placed on a well-known offer wall. Fraudster using SDK spoofing also send a burst of conversions when they figure out how to fool attribution SDKs.