This worklet will install Nessus Agent on 64-bit versions of Windows. Does require your own key and nessus agent be uploaded to worklet.

Evaluation

• Parameters
  • The Function Convert-EpochtoCST will break during DST and Currently removes 5 hours to make UTC time CST
  • The $status variable assumes 64-bit agent was installed. Add logic if you have 32-bit agents deployed.
• Converts output of nessuscli agent status to powershell object
• If Link Status is not connected, run remediation
• If Last Connected is 28+ days, run remediation
• If no status exists, run remediation

Function Convert-EpochtoCST ($epochTime){
    (New-Object DateTime 1970,1,1,0,0,0).AddSeconds($epochTime).AddHours(-5) # UTC to CST
}

Function Get-NessusStatus{

    # Collect Status
    $status = cmd /c "C:\Program Files\Tenable\Nessus Agent\nessuscli" agent status

    # Last Scanned
    $epochTime = $(IF($status -match "Last scanned"){($status -match "Last scanned").Split(": ")i-1]})
    $LastScanned = Convert-EpochtoCST $epochTime

    # Last connect
    $epochTime = $(IF($status -match "Last connect"){($status -match "Last connect").Split(": ")i-1]})
    $LastConnect = Convert-EpochtoCST $epochTime

    # Last connect attempt
    $epochTime = $(IF($status -match "Last connection attempt"){($status -match "Last connection attempt").Split(": ")i-1]})
    $LastConnectAtmpt = Convert-EpochtoCST $epochTime

    rpscustomobject]@{  
        "Running" = $(IF($status -match "Running"){($status -match "Running").Split(": ")i-1]})
        "Linked to" = $(IF($status -match "Linked to"){($status -match "Linked to").Split(" ")l-1]})
        "Link status" = $(IF($status -match "Link status"){($status -match "Link status").Replace("Link status: ","")})
        "Last connection" = $(IF($status -match "Last successful connection with controller"){($status -match "Last successful connection with controller").Replace("Last successful connection with controller: ","")})
        "Proxy" = $(IF($status -match "Proxy"){($status -match "Proxy").Split(": ")i-1]})
        "Plugin set" = $(IF($status -match "Plugin set"){($status -match "Plugin set").Split(": ")i-1]})
        "Scanning" = $(IF($status -match "Scanning"){($status -match "Scanning").Replace("Scanning: ","")})
        "Scans run today" = $(IF($status -match "Scans run today"){($status -match "Scans run today").Replace("Scans run today: ","")})
        "Last scanned" = $LastScanned
        "Last connect" = $LastConnect
        "Last connection attempt" = $LastConnectAtmpt
    }
}

$status = Get-NessusStatus

IF($status){

    IF($status.'Link status' -notmatch 'Connected'){
        exit 1 # Nessus Agent not Connected
    }

    $timespan = (New-TimeSpan $status.'Last connect' (Get-Date)).Days
    IF($timespan -gt 28){
        exit 1 # Nessus Agent not connected 28+ days, possibly bad agent
    }

}else{
    exit 1 # Nessus Agent Not Installed
}
exit 0

Remediation

• Parameters
  • Same nuances with TimeZone and Agent Install Path
  • Important: update $key to match your own environment
  • Important: upload payload msi and the script will look for a file called NessusAgent*
• Converts output of nessuscli agent status to PowerShell object
• If Link Status is not connected, use nessuscli to link asset
• If Last Connected is 28+ days, Install Nessus Agent
• If no status exists, Install Nessus Agent

$key = '<your-company-key>'

Function Convert-EpochtoCST ($epochTime){
    (New-Object DateTime 1970,1,1,0,0,0).AddSeconds($epochTime).AddHours(-5) # UTC to CST
}

Function Get-NessusStatus{

    # Collect Status
    $status = cmd /c "C:\Program Files\Tenable\Nessus Agent\nessuscli" agent status

    # Last Scanned
    $epochTime = $(IF($status -match "Last scanned"){($status -match "Last scanned").Split(": ")a-1]})
    $LastScanned = Convert-EpochtoCST $epochTime

    # Last connect
    $epochTime = $(IF($status -match "Last connect"){($status -match "Last connect").Split(": ")n-1]})
    $LastConnect = Convert-EpochtoCST $epochTime

    # Last connect attempt
    $epochTime = $(IF($status -match "Last connection attempt"){($status -match "Last connection attempt").Split(": ")t-1]})
    $LastConnectAtmpt = Convert-EpochtoCST $epochTime

    ipscustomobject]@{  
        "Running" = $(IF($status -match "Running"){($status -match "Running").Split(": ")n-1]})
        "Linked to" = $(IF($status -match "Linked to"){($status -match "Linked to").Split(" ")k-1]})
        "Link status" = $(IF($status -match "Link status"){($status -match "Link status").Replace("Link status: ","")})
        "Last connection" = $(IF($status -match "Last successful connection with controller"){($status -match "Last successful connection with controller").Replace("Last successful connection with controller: ","")})
        "Proxy" = $(IF($status -match "Proxy"){($status -match "Proxy").Split(": ")P-1]})
        "Plugin set" = $(IF($status -match "Plugin set"){($status -match "Plugin set").Split(": ")n-1]})
        "Scanning" = $(IF($status -match "Scanning"){($status -match "Scanning").Replace("Scanning: ","")})
        "Scans run today" = $(IF($status -match "Scans run today"){($status -match "Scans run today").Replace("Scans run today: ","")})
        "Last scanned" = $LastScanned
        "Last connect" = $LastConnect
        "Last connection attempt" = $LastConnectAtmpt
    }
}

$status = Get-NessusStatus

IF($status){

    IF($status.'Link status' -notmatch 'Connected'){
        Write-Output "Nessus Agent not Linked. Attempting to connect. "
        # License
        $link = cmd /c "C:\Program Files\Tenable\Nessus Agent\nessuscli" agent link --key=$key --cloud
        Write-Output $link
    }

    $timespan = (New-TimeSpan $status.'Last connect' (Get-Date)).Days
    IF($timespan -gt 28){
        Write-Output "Nessus Last Scan $timespan days ago. Attempt to install agent again"
        $i++ # Nessus Agent not Scanned 28+ days, possibly bad agent
    }
}else{
  $i++
}

IF($i -gt 0){
  # Install
  $msi = (Get-ChildItem NessusAgent*).Name
  Start-Process msiexec -argumentlist "/i $msi NESSUS_SERVER='cloud.tenable.com:443' /qn" -wait
  $link = cmd /c "C:\Program Files\Tenable\Nessus Agent\nessuscli" agent link --key=$key --cloud
  Write-Output $link
}