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Author

  • Schinzel, Sebastian (28)
  • Dresen, Christian (9)
  • Ising, Fabian (9)
  • Saatjohann, Christoph (8)
  • Poddebniak, Damian (6)
  • Schwenk, Jörg (5)
  • Willing, Markus (5)
  • Haverkamp, Uwe (4)
  • Müller, Jens (4)
  • Somorovsky, Juraj (4)
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  • Cardiac Implantable Devices (1)
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  • docx (1)
  • networked computer tomography scanner (1)

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  • Elektrotechnik und Informatik (ETI) (28)

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Information leakage behind the curtain: Abusing anti-EMI features for covert communication (2016)
Bauer, Johannes ; Schinzel, Sebastian ; Felix, C. ; Freiling, Andreas
WAFFle: Fingerprinting Filter Rules of Web Application Firewalls (2012)
Schmitt, Isabell ; Schinzel, Sebastian
Security mechanisms of a legal peer-to-peer file sharing system (2008)
Ebinger, Peter ; Schinzel, Sebastian ; Schmuckler, Martin
kAFL: Hardware-Assisted Feedback Fuzzing for OS Kernels (2017)
Schumilo, Sergej ; Aschermann, Cornelius ; Gawlik, Robert ; Schinzel, Sebastian ; Holz, Thorsten
Efail: Breaking S/MIME and OpenPGP Email Encryption using Exfiltration Channels (2018)
Poddebniak, Damian ; Dresen, Christian ; Müller, Jens ; Ising, Fabian ; Schinzel, Sebastian ; Friedberg, Simon ; Somorovsky, Juraj ; Schwenk, Jörg
Practical Decryption exFiltration: Breaking PDF Encryption (2019)
Müller, Jens ; Ising, Fabian ; Mldadenov, Vladislav ; Mainka, Christian ; Schinzel, Sebastian ; Schwenk, Jörg
The Portable Document Format, better known as PDF, is one of themost widely used document formats worldwide, and in order to en-sure information confidentiality, this file format supports documentencryption. In this paper, we analyze PDF encryption and showtwo novel techniques for breaking the confidentiality of encrypteddocuments. First, we abuse the PDF feature ofpartially encrypteddocuments to wrap the encrypted part of the document withinattacker-controlled content and therefore, exfiltrate the plaintextonce the document is opened by a legitimate user. Second, we abusea flaw in the PDF encryption specification to arbitrarily manipulateencrypted content. The only requirement is that a single block ofknown plaintext is needed, and we show that this is fulfilled bydesign. Our attacks allow the recovery of the entire plaintext of en-crypted documents by using exfiltration channels which are basedon standard compliant PDF properties.We evaluated our attacks on 27 widely used PDF viewers andfound all of them to be vulnerable. We responsibly disclosed thevulnerabilities and supported the vendors in fixing the issue
Analysis and consequences of an imaging process concerning the cyber security of a networked computer tomography scanner (2018)
Gierling, Markus ; Dresen, Christian ; Eich, Hans ; Mittman, Karin ; Schinzel, Sebastian ; Haverkamp, Uwe
"I don’t know why I check this...'' - Investigating Expert Users' Strategies to Detect Email Signature Spoofing Attacks (2022)
Mayer, Peter ; Poddebniak, Damian ; Fischer, Konstantin ; Brinkmann, Marcus ; Somorovsky, Juraj ; Schinzel, Sebastian ; Volkamer, Melanie
OpenPGP is one of the two major standards for end-to-end email security. Several studies showed that serious usability issues exist with tools implementing this standard. However, a widespread assumption is that expert users can handle these tools and detect signature spoofing attacks. We present a user study investigating expert users' strategies to detect signature spoofing attacks in Thunderbird. We observed 25 expert users while they classified eight emails as either having a legitimate signature or not. Studying expert users explicitly gives us an upper bound of attack detection rates of all users dealing with PGP signatures. 52% of participants fell for at least one out of four signature spoofing attacks. Overall, participants did not have an established strategy for evaluating email signature legitimacy. We observed our participants apply 23 different types of checks when inspecting signed emails, but only 8 of these checks tended to be useful in identifying the spoofed or invalid signatures. In performing their checks, participants were frequently startled, confused, or annoyed with the user interface, which they found supported them little. All these results paint a clear picture: Even expert users struggle to verify email signatures, usability issues in email security are not limited to novice users, and developers may need proper guidance on implementing email signature GUIs correctly.
Behavioral responses to a cyber attack in a hospital environment (2021)
Willing, Markus ; Dresen, Christian ; Gerlitz, Eva ; Haering, Maximilian ; Smith, Matthew ; Binnewies, Carmen ; Guess, Tim ; Haverkamp, Uwe ; Schinzel, Sebastian
Technical and organizational steps are necessary to mitigate cyber threats and reduce risks. Human behavior is the last line of defense for many hospitals and is considered as equally important as technical security. Medical staff must be properly trained to perform such procedures. This paper presents the first qualitative, interdisciplinary research on how members of an intermediate care unit react to a cyberattack against their patient monitoring equipment. We conducted a simulation in a hospital training environment with 20 intensive care nurses. By the end of the experiment, 12 of the 20 participants realized the monitors’ incorrect behavior. We present a qualitative behavior analysis of high performing participants (HPP) and low performing participants (LPP). The HPP showed fewer signs of stress, were easier on their colleagues, and used analog systems more often than the LPP. With 40% of our participants not recognizing the attack, we see room for improvements through the use of proper tools and provision of adequate training to prepare staff for potential attacks in the future.
LanDscAPe: Exploring LDAP Weaknesses and Data Leaks at Internet Scale (2024)
Kaspereit, Jonas ; Öndarö, Gurur ; Luvizotto Cesar, Gustavo ; Ebbers, Simon ; Ising, Fabian ; Saatjohann, Christoph ; Jonker, Mattijs ; Holz, Ralph ; Schinzel, Sebastian
The Lightweight Directory Access Protocol (LDAP) is the standard technology to query information stored in directories. These directories can contain sensitive personal data such as usernames, email addresses, and passwords. LDAP is also used as a central, organization-wide storage of configuration data for other services. Hence, it is important to the security posture of many organizations, not least because it is also at the core of Microsoft’s Active Directory, and other identity management and authentication services. We report on a large-scale security analysis of deployed LDAP servers on the Internet. We developed LanDscAPe, a scanning tool that analyzes security-relevant misconfigurations of LDAP servers and the security of their TLS configurations. Our Internet-wide analysis revealed more than 10k servers that appear susceptible to a range of threats, including insecure configurations, deprecated software with known vulnerabilities, and insecure TLS setups. 4.9k LDAP servers host personal data, and 1.8k even leak passwords. We document, classify, and discuss these and briefly describe our notification campaign to address these concerning issues.
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