decode javascript with Revelo
Updated on April 16, 2016
If you strip away the URL parameters and visit the site, you should see something like this.
The Javascript base64-decodes a string that’s been reversed. You can see that there’s an eval at the end which executes the result. Before I introduce a new tool, let me show you how to quickly deobfuscate this with Revelo via two methods. With the first method, paste in the script, choose “Redirect Eval to Action”, then click on “Execute”.
Click on the “Results” tab to get the results.
Copy that script and paste it on the main tab. Revelo needs to see the <script></script> tags so make sure it’s there. We can see that the script is packed with eval at the beginning but since this script is packed multiple times, you will notice it has “eval” near the end of the script too. We need to tell Revelo to catch the “eval” at the beginning so click on Options > Replace Starting at Top. Leave the deobfuscation method as-is then click on “Execute” again.
Click on the “Results” tab to get the results. You need to do this a couple more times before you end up with this. You will see the script now using “document.write” so choose “Redirect Do.Write to Action”.
Finally, we get to the deobfuscated script.
If you just want to get to the final redirect URL without going through the above steps then you can select either “Capture HTTP Request via Proxy” or “Capture HTTP Request via IE”. This is the second method.
With either option, Revelo will execute the script and block the HTTP request to the website then show you where it was going to go. This keeps your computer safe but you should always run Revelo in a VM just in case these scripts use exploits or call another app to make the HTTP request.
The Javascript base64-decodes a string that’s been reversed. You can see that there’s an eval at the end which executes the result. Before I introduce a new tool, let me show you how to quickly deobfuscate this with Revelo via two methods. With the first method, paste in the script, choose “Redirect Eval to Action”, then click on “Execute”.
Click on the “Results” tab to get the results.
Copy that script and paste it on the main tab. Revelo needs to see the <script></script> tags so make sure it’s there. We can see that the script is packed with eval at the beginning but since this script is packed multiple times, you will notice it has “eval” near the end of the script too. We need to tell Revelo to catch the “eval” at the beginning so click on Options > Replace Starting at Top. Leave the deobfuscation method as-is then click on “Execute” again.
Click on the “Results” tab to get the results. You need to do this a couple more times before you end up with this. You will see the script now using “document.write” so choose “Redirect Do.Write to Action”.
Finally, we get to the deobfuscated script.
If you just want to get to the final redirect URL without going through the above steps then you can select either “Capture HTTP Request via Proxy” or “Capture HTTP Request via IE”. This is the second method.
With either option, Revelo will execute the script and block the HTTP request to the website then show you where it was going to go. This keeps your computer safe but you should always run Revelo in a VM just in case these scripts use exploits or call another app to make the HTTP request.