The virus spreads within applications (Word to Word, Excel to Excel) as well as drops infected files to another application (Word to Excel and Excel to Word).
The virus uses the same VBA program code under both Word and Excel.
The virus uses Import/Export VisualBasic functions: the virus exports its Basic code to the C:\LO.SYS file, and then imports it into documents.
To spread from Word to Excel and vice versa, the virus uses a trick with auto-loading ability of Word and Excel. These applications load templates (Word) and sheets (Excel) from startup directory: to infect Word from Excel the virus creates new NORMAL.DOT (Word) and PERSONAL.XLS (Excel) files in startup directory.
NORMAL.DOT and PERSONAL.XLS contain a small loader program. This loader imports the actualy virus code from the C:\LO.SYS file to NORMAL.DOT or PERSONAL.XLS, depending on the platform.
The virus disables the Tools/Macro, Tools/Options, File/Templates and View/VBCode menu items as well as turns off VisualBasicEditor and VirusProtection. This is done in order to protect the virus from being analyzed. The virus also changes VirusProtection instructions in the system registry.
On 26th of any month, Teocatl displays a dialog box and deletes all files in the current directory. The following text is displayed:
Strange Days by Reptile/29A Strange days have found us Strange days have tracked us down They're going to destroy...
[Analysis by Eugene Kaspersky]