Flags contracts which calls external contract during token transfers, approvals and allowances

Context and definitions

External call: External calls are function calls that a smart contract makes to another smart contract.

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From a security perspective, do not trust external smart contracts!!

Use caution when making external calls

• Calls to untrusted contracts can introduce several unexpected risks or errors.
• External calls may execute malicious code in that contract or any other contract that it depends upon.
• As such, every external call should be treated as a potential security risk.
• The use of external calls specially in transfers, approvals and allowances should be noted with high risk.

Reference article from Blockfence

$32M Stolen: Over 1,300 Fake Tokens Rugged (Full Investigation)

Look out for external calls being done to other contracts in functions like _transfer(), approve(), etc

https://etherscan.io/token/0x25e0d545b4733e051e2edca12ae5b7366d773549#code

• Inside _transfer() external call to contract hhxnnadsa is being done to get balances, which is the root source of the underlying scam.
• The external call tampers balances