You may get an email apparently from someone you know, asking you to open a file on Dropbox ... and, when you follow the link, you will be asked to log in using an email address and password.
NEVER do this - if you do scammers will have full access to your email account as you have just given them your account password!
If you have responded, everything in that email account will have been available to the wrong people.
You need to change your email account password immediately.
Any passwords that have been sent to you at that email account will have to be changed too.
Eynsham Futures does use Dropbox to exchange large files but you will NEVER need to log in. All our links to Dropbox should open the file directly and will have been sent as part of an email which explains what the file is.