hydra.helsinki.fi has never been the right site: you should use
ftp.cs.helsinki.fi instead. It _used_ to physically be hydra a long
time ago, and even quite recently hydra had the ftp directory
nfs-mounted so that hydra still accepted the accesses. But they have
made changes in how the NFS setup works around here and now hydra no
longer even mounts the ftp directory (that may change again, but
ftp.cs.helsinki.fi will at least always be valid)
Linus