Powershell download file from base64 url

 1title: Powershell download file from base64 url
 2status: experimental
 3description: Powershell download file from base64 url
 4author: Joe Security
 5date: 2020-04-13
 6id: 200072
 7threatname:
 8behaviorgroup: 1
 9classification: 8
10mitreattack:
11
12logsource:
13    category: process_creation
14    product: windows
15detection:
16    selection:
17        CommandLine:
18            - '*.downloadfile([system.text.encoding]::ascii.getstring([system.convert]::frombase64string(*'
19    condition: selection
20level: critical