Johannes Ullrich

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Network intrusions have been a fact of life in the Internet for many years. However, as is the case with many other types of Internet-wide phenomena, gaining insight into the <i>global</i> characteristics of intrusions is challenging. In this paper we address this problem by systematically analyzing a set of firewall logs collected over four months from(More)
The notion of blacklisting communication sources has been a well-established defensive measure since the origins of the Internet community. In particular, the practice of compiling and sharing lists of the worst offenders of unwanted traffic is a blacklisting strategy that has remained virtually unquestioned over many years. But do the individuals who(More)
Need for cognition (NFC) refers to an individual's tendency to engage in and enjoy effortful cognitive processing. So far, little attention has been paid to a systematic evaluation of the distinctiveness of NFC from traits with similar conceptualization and from intelligence. The present research contributes to filling this gap by examining the relation of(More)
Guided by the Needs-Based Model of Reconciliation, we hypothesized that being a member of a victimized group would be associated with a threat to the status and power of one's ingroup, whereas being a member of a perpetrating group would threaten the image of the ingroup as moral and socially acceptable. A social exchange interaction through which victims(More)
Three general properties of social stereotypes are the perception of differences between ingroups and outgroups (intergroup differentiation), the perception of ingroups as having more desirable attributes than outgroups (ingroup favoritism), and the greater accuracy of ingroup perceptions (differential accuracy). We present and test an inductive-reasoning(More)
This article extends research on leader procedural fairness as well as the social identity model of leadership effectiveness (SIMOL) by demonstrating that leader prototypicality can act as a substitute for procedural fairness. Although procedural fairness in general and voice in particular have been found to have a robust positive influence on leader(More)
In this article, we develop a perspective on social change as cooperation between advantaged and disadvantaged groups to facilitate not only redistribution of power and wealth but also restoration of threatened identity dimensions. We argue that disadvantaged groups experience threats to their agency whereas advantaged groups experience threats to their(More)
Network security has been a serious concern for many years. For example, firewalls often record thousands of exploit attempts on a daily basis. Network administrators could benefit from information on potential aggressive attack sources, as such information can help to proactively defend their networks. For this purpose, several large-scale information(More)
We use regulatory focus theory to derive specific predictions regarding the differential relationships between regulatory focus and commitment. We estimated a structural equation model using a sample of 520 private and public sector employees and found in line with our hypotheses that (a) promotion focus related more strongly to affective commitment than(More)
Ambivalence researchers often collapse separate measures of positivity and negativity into a single numerical index of ambivalence and refer to it as objective, operative, or potential ambivalence. The authors argue that this univariate approach to ambivalence models undermines the validity of subsequent statistical analyses because it confounds the effects(More)