2009/1/11 Robert Brockway <rob...@timetraveller.org>: > On Sun, 11 Jan 2009, Dotan Cohen wrote: > >> On a machine that I have root access to, how can I see who is logged >> into the machine? Specifically, I suspect that a malicious entity is >> logging on in a compromised account over SSH, even while the account's >> user is sitting at the machine and logged in, so if I can catch two >> simultaneous login sessions (one on the physical hardware, one over >> ssh) then I can be sure. Thanks. > > w and who have been mentioned. I generally prefer finger (which runs quite > happily locally without a fingerd to connect to). > > You probably also want to look at last[1] which will show a history of when > users were logged in. > > But... > > If you really think the a/c has been compromised then don't wait for the > baddie to log in again. Lock the account. Scan the box for anomalies (eg, > checkrootkit) and take a particular interest in that a/c. > > If you don't find any evidence that the baddie broke root then may wish to > reset the a/c password and move on. If you find any evidence that the > baddie broke root then best practice is to restore the box from known good > backups. You can never guarantee that you found all of the backdoors that a > cracker may have left on a system. > > I'll stop now as there is a lot more I could say on this topic but it isn't > necessary at this stage. > > [1] I comment out the entry concerning wtmp in /etc/logrotate.conf as this > allows the login history to remain indefinitely. Even for multi-user boxes > that have been running for years I haven't found a problem doing this. wtmp > is tiny so disk space is hardly an issue. > > Cheers, > > Rob >
Thanks, Rob. Although I found no evidence of the breakin that I had suspected, I changed the password anyway. Like fine underwear, passwords should be changed every few months for good measure. -- Dotan Cohen http://what-is-what.com http://gibberish.co.il א-ב-ג-ד-ה-ו-ז-ח-ט-י-ך-כ-ל-ם-מ-ן-נ-ס-ע-ף-פ-ץ-צ-ק-ר-ש-ת ا-ب-ت-ث-ج-ح-خ-د-ذ-ر-ز-س-ش-ص-ض-ط-ظ-ع-غ-ف-ق-ك-ل-م-ن-ه-و-ي А-Б-В-Г-Д-Е-Ё-Ж-З-И-Й-К-Л-М-Н-О-П-Р-С-Т-У-Ф-Х-Ц-Ч-Ш-Щ-Ъ-Ы-Ь-Э-Ю-Я а-б-в-г-д-е-ё-ж-з-и-й-к-л-м-н-о-п-р-с-т-у-ф-х-ц-ч-ш-щ-ъ-ы-ь-э-ю-я ä-ö-ü-ß-Ä-Ö-Ü
