  EOSIO has become one of the most popular blockchain platforms since its
mainnet launch in June 2018. In contrast to the traditional PoW-based systems
(e.g., Bitcoin and Ethereum), which are limited by low throughput, EOSIO is the
first high throughput Delegated Proof of Stake system that has been widely
adopted by many applications. Although EOSIO has millions of accounts and
billions of transactions, little is known about its ecosystem, especially
related to security and fraud. In this paper, we perform a large-scale
measurement study of the EOSIO blockchain and its associated DApps. We gather a
large-scale dataset of EOSIO and characterize activities including money
transfers, account creation and contract invocation. Using our insights, we
then develop techniques to automatically detect bots and fraudulent activity.
We discover thousands of bot accounts (over 30\% of the accounts in the
platform) and a number of real-world attacks (301 attack accounts). By the time
of our study, 80 attack accounts we identified have been confirmed by DApp
teams, causing 828,824 EOS tokens losses (roughly 2.6 million US\$) in total.
