Astroturfing attacks use automated accounts to artificially propel a chosen keyword to the top of Twitter trending topics. Lateral astroturfing is a sophisticated subset of such attacks in which the automated tweets 1) are posted by compromised accounts making it more effective and 2) are deleted immediately after they are created to evade detection. We present the first large-scale analysis of lateral astroturfing attacks, involving 20,000 astroturfing accounts that were used between February 2019 and June 2019 to manipulate 3,710 unique keywords --- at least 10% of daily trending topics in the region analyzed. Lateral astroturfing pollutes trending topics; allows for the manipulation of users' opinions; and permits content that could otherwise be filtered by the platform, such as illicit advertisements. Our results aid in understanding user manipulation on social media and more generally shed light on the type of adversarial behavior that arises to evade detection.