4,377 research outputs found
Holmes: An Efficient and Lightweight Semantic Based Anomalous Email Detector
Email threat is a serious issue for enterprise security, which consists of
various malicious scenarios, such as phishing, fraud, blackmail and
malvertisement. Traditional anti-spam gateway commonly requires to maintain a
greylist to filter out unexpected emails based on suspicious vocabularies
existed in the mail subject and content. However, the signature-based approach
cannot effectively discover novel and unknown suspicious emails that utilize
various hot topics at present, such as COVID-19 and US election. To address the
problem, in this paper, we present Holmes, an efficient and lightweight
semantic based engine for anomalous email detection. Holmes can convert each
event log of email to a sentence through word embedding then extract
interesting items among them by novelty detection. Based on our observations,
we claim that, in an enterprise environment, there is a stable relation between
senders and receivers, but suspicious emails are commonly from unusual sources,
which can be detected through the rareness selection. We evaluate the
performance of Holmes in a real-world enterprise environment, in which it sends
and receives around 5,000 emails each day. As a result, Holmes can achieve a
high detection rate (output around 200 suspicious emails per day) and maintain
a low false alarm rate for anomaly detection
Effects of Cations and PH on Antimicrobial Activity of Thanatin and s-Thanatin against _Escherichia coli_ ATCC25922 and _B. subtilis_ ATCC 21332
Thanatin and s-thanatin were insect antimicrobial peptides which have shown potent antimicrobial activities on a variety of microbes. In order to investigate the effect of cations and pH on the activity of these peptides against Gram-negative bacteria and Gram-positive bacteria, the antimicrobial activities of both peptides were studied in increasing concentrations of monovalent cations (K^+^ and Na^+^), divalent cations (Ca^2+^ and Mg^2+^) and H^+^. The NCCLS broth microdilution method showed that both peptides were sensitive to the presence of cations. The divalent cations showed more antagonized effect on the activity against Gram-negative bacteria than the monovalent cations, since the two peptides lost the ability to inhibit bacterial growth at a very low concentration. In addition, the activities of both peptides tested were not significantly affected by pH. Comparing to studies of other antibacterial peptide activities, our data support a hypothesis that positive ions affect the sensitivity to cation peptides
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