在@''@之间插入大段powershell代码，并将一下脚本放入powershell中执行
注意@'后加换行，'@前加换行

$command = @'
$lastUpdate = (Get-MpComputerStatus).AntivirusSignatureLastUpdated
"病毒定义最后更新: $($lastUpdate.ToLocalTime())"
'@
$bytes = [System.Text.Encoding]::Unicode.GetBytes($command)
$encodedCommand = [Convert]::ToBase64String($bytes)
Write-Output $encodedCommand

生成一下base64编码，（非加密）

JABsAGEAcwB0AFUAcABkAGEAdABlACAAPQAgACgARwBlAHQALQBNAHAAQwBvAG0AcAB1AHQAZQByAFMAdABhAHQAdQBzACkALgBBAG4AdABpAHYAaQByAHUAcwBTAGkAZwBuAGEAdAB1AHIAZQBMAGEAcwB0AFUAcABkAGEAdABlAGQACgAiAMV10muaW0lOAGcOVPRmsGU6ACAAJAAoACQAbABhAHMAdABVAHAAZABhAHQAZQAuAFQAbwBMAG8AYwBhAGwAVABpAG0AZQAoACkAKQAiAA==

将编码放在一下代码中

powershell -EncodedCommand ""

powershell -EncodedCommand "JABsAGEAcwB0AFUAcABkAGEAdABlACAAPQAgACgARwBlAHQALQBNAHAAQwBvAG0AcAB1AHQAZQByAFMAdABhAHQAdQBzACkALgBBAG4AdABpAHYAaQByAHUAcwBTAGkAZwBuAGEAdAB1AHIAZQBMAGEAcwB0AFUAcABkAGEAdABlAGQACgAiAMV10muaW0lOAGcOVPRmsGU6ACAAJAAoACQAbABhAHMAdABVAHAAZABhAHQAZQAuAFQAbwBMAG8AYwBhAGwAVABpAG0AZQAoACkAKQAiAA=="

主要注意空格和使用英文符号。