Log Public IP Changes

by David | Sep 22, 2021 | Information Technology, PowerShell

This little script logs public IP address changes. The original design was to email out. I’ll make sure to point out when and where to put that code. So the idea is simple. It checks to see if it’s public IP address has changed using an invoke-webrequest. If it has changed, it checks to see if a log has been made. If it has been made, it updates the log, if it hasn’t been made, it creates the log. Then when the IP address changes back, it backs up the logs and stops. Lets take a look at the script.

The Script

Param (
    [string]$IPAddress = "Your IP Address"
)  
$IP = (invoke-webrequest -Uri "http://ifconfig.me/ip" -UseBasicParsing).content
If (!(Test-Path C:\temp)) { New-Item -Path "c:\temp" -ItemType Directory }
if (!($IP -like "$IPAddress")) {
    if (!(Test-Path c:\temp\IPTrigger.log )) {

#Email Code Goes Here

        $Datetime = (Get-Date).ToString("yyyy-MM-dd_HH-mm")
        "Datetime,IP" > c:\temp\IPTrigger.log
        "$datetime,$IP" >> c:\temp\IPTrigger.log 
    }
    else {
        $Datetime = (Get-Date).ToString("yyyy-MM-dd_HH-mm")
        "$datetime,$IP" >> c:\temp\IPTrigger.log 
    }
}
else {
    if (Test-Path c:\temp\IPTrigger.log) {
        $Datetime = (Get-Date).ToString("yyyy-MM-dd_HH-mm")
        Copy-Item -Path c:\temp\IPTrigger.log -Destination "c:\temp\IPTrigger_$($datetime).log.bak"
        Remove-Item -Path  c:\temp\IPTrigger.log

#Email Code goes here with attachment of the log bak. 

    }
}

The Breakdown

We grab the IP address from the Paramters. This way you can have the script called Public-IPChecker -IPAddress Something from your task scheduler. After we get what the IP Address should be we get what It is with the Invoke-webrequest command.

$IP = (invoke-webrequest -Uri "http://ifconfig.me/ip" -UseBasicParsing).content

There are a hand full of sites that grabs the IP address for you. I personally like Ifconfig.me because it places the IP address as the content. Thus no sorting through the HTML to get the IP address.

Next we ask if it’s the IP address. Then we ask if the log has been made.

if (!($IP -like "$IPAddress")) {
    if (!(Test-Path c:\temp\IPTrigger.log )) {}
}

If it doesn’t exist, we create it by getting the DateTime into a file friendly format. and Piping that information into the log file along with the current IP address.

$Datetime = (Get-Date).ToString("yyyy-MM-dd_HH-mm")
"Datetime,IP" > c:\temp\IPTrigger.log
"$datetime,$IP" >> c:\temp\IPTrigger.log 

If it does exist, we just update the log file using the same code but this time we remove the “Datetime,IP” part.

$Datetime = (Get-Date).ToString("yyyy-MM-dd_HH-mm")
"$datetime,$IP" >> c:\temp\IPTrigger.log 

If the IP addresses do match then we test to see if the log file is there. If it is there we create a bak of the log file and remove the old one. This is when you can send an email saying it’s back up. If it doesn’t exist, we do nothing.

if (Test-Path c:\temp\IPTrigger.log) {
        $Datetime = (Get-Date).ToString("yyyy-MM-dd_HH-mm")
        Copy-Item -Path c:\temp\IPTrigger.log -Destination "c:\temp\IPTrigger_$($datetime).log.bak"
        Remove-Item -Path  c:\temp\IPTrigger.log
}

That’s the full script in a nutshell.