One question we frequently get is "where can I get the latest IOS for a Cisco device?" It is common practice to purchase Cisco equipment on eBay and you will almost certainly have outdated firmware on the devices you receive. There are a few answers to that question, but the official answer is that in order to receive software updates, the Cisco device in question must have a current Cisco SmartNet agreement. If you aren't familiar with SmartNet, it is Cisco's maintenance and warranty service. Cisco will allow you to enroll almost any device (including extremely old equipment and even equipment purchased on eBay) for a fixed fee (typically 10-20% of the device's price) that is paid annually. Once your device is covered, you will then be able to receive software updates directly from Cisco's website as well as get hardware warranty support in the event of failed equipment.
Keep in mind that Cisco SmartNet contracts are tied to the company that purchases them and are non-transferable. As a result, any equipment purchased second-hand will not be covered by SmartNet and will require you to re-subscribe.
You will find many people posting IOS images on the internet for download. The attraction here is that you can obtain the software for free. However, there are two main problems with this:

  1. You are downloading unlicensed software which is a violation of the Cisco terms of service. It is the same as bootlegging a copy of Windows or pirating movies online.
  2. The software may have been tampered with. This is especially true when dealing with security devices.
    So while googling for IOS images is certainly an option, the only way to get new images in a legal and safe manner is through a Cisco SmartNet agreement.