1. Introduction

Alertra ASL scripts are used by Alertra to perform a check of a given Internet resource. ASL provides mechanisms to specify the Internet resource, provide parameters to the various checks made, and check the results. ASL scripts run on the Alertra's network of remote monitoring stations, no software is installed on customer servers to run ASL scripts.

1.1. Features

ASL can check the following types of Internet resources:

• FTP File Transfer Protocol Test retrieving files from FTP servers using anonymous logins or user specified credentials.
• HTTP/HTTPS 1.0 and 1.1 Check your web sites with the ability to handle forms, check for changes to pages, and follow redirections.
• IMAP4 Connect, get message count, delete messages.
• MySQL Connect, execute queries, retreive results.
• Nameserver Query to resolve domain name to IP.
• PING Send ICMP requests to a server.
• POP3 Connect, get message count, delete messages.
• SMTP Connect, send message.
• SSH Connect, login.
• TELNET Connect, login.
• TCP Sockets Using the tcp, send, recv primitives you can test virtually any socket based Internet resource.

Webmasters are continually on the watch for hackers and the possible defacement of their websites. ASL provides several means of detecting that changes have been made to the site:

• Size Checking ASL can check the size of the content returned from any of the protocol commands and inform you when the size is not correct.
• Content Checking ASL can also scan the returned content to make sure a particular string is found or not found depending on your requirements.
• Digest Developed by NIST, SHA computes a one-way hash of the content returned from an HTTP or FTP commands. This hash is like a fingerprint for the content; any changes to the content will result in a different hash. With ASL you can detect changes to the hash and generate an alert accordingly.

1.2. Getting Started

The best way to get started with ASL is to read the Tutorial. In it you will find examples of several common scripts that you can use as a basis for your own scripts. There are also several articles available on site under the heading Scripting: Unlock the Power of Alertra.